1
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Shan M, Li S, Yang Y, Zhao D, Li J, Nie L, Wu Z, Zhou Y, Zheng L, Kang B, Wu T, Chen X. Anisotropic Spin Fluctuations Induced by Spin-Orbit Coupling in a Misfit Layer Compound (LaSe) 1.14(NbSe 2). ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2024:e2403824. [PMID: 39206691 DOI: 10.1002/advs.202403824] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/12/2024] [Revised: 08/02/2024] [Indexed: 09/04/2024]
Abstract
Spin-orbit coupling (SOC) has significant effects on the superconductivity and magnetism of transition metal dichalcogenides (TMDs) at the 2D limit. Although 2D TMD samples possess many exotic properties different from those of bulk samples, experimental characterization in this field is still limited, especially for magnetism. Recent studies have revealed that bulk misfit layer compounds (MLCs) with (LaSe)1.14(NbSe2)n = 1,2 exhibit an Ising superconductivity similar to that of heavily electron-doped NbSe2 monolayers. This offers an opportunity to study the effect of SOC on the magnetism of 2D TMDs. Here, the possible SOC effect in (LaSe)1.14(NbSe2) is investigated by measuring nuclear magnetic resonance (NMR) and electrical transport. It is found that the LaSe layer not only functions as a charge reservoir for transferring electrons into the NbSe2 layer but also remarkably influences the local electronic environment around the 93Nb nuclei. More importantly, the significant SOC induces both a weak antilocalization (WAL) effect and anisotropic spin fluctuations in noncentrosymmetric NbSe2 layers. The present work contributes to a deep understanding of the role of the SOC effect in 2D TMDs and supports MCLs as an intriguing platform for exploring exotic physical properties within the 2D limit.
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Affiliation(s)
- Min Shan
- Hefei National Research Center for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui, 230026, China
| | - Shunjiao Li
- Hefei National Research Center for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui, 230026, China
| | - Ye Yang
- Hefei National Research Center for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui, 230026, China
| | - Dan Zhao
- Hefei National Research Center for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui, 230026, China
| | - Jian Li
- Hefei National Research Center for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui, 230026, China
| | - Linpeng Nie
- Hefei National Research Center for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui, 230026, China
| | - Zhimian Wu
- Hefei National Research Center for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui, 230026, China
| | - Yanbing Zhou
- Hefei National Research Center for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui, 230026, China
| | - Lixuan Zheng
- Hefei National Research Center for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui, 230026, China
| | - Baolei Kang
- Hefei National Research Center for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui, 230026, China
| | - Tao Wu
- Hefei National Research Center for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui, 230026, China
- CAS Key Laboratory of Strongly-coupled Quantum Matter Physics, Department of Physics, University of Science and Technology of China, Hefei, Anhui, 230026, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, 210093, China
- Hefei National Laboratory, University of Science and Technology of China, Hefei, 230088, China
| | - Xianhui Chen
- Hefei National Research Center for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui, 230026, China
- CAS Key Laboratory of Strongly-coupled Quantum Matter Physics, Department of Physics, University of Science and Technology of China, Hefei, Anhui, 230026, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, 210093, China
- Hefei National Laboratory, University of Science and Technology of China, Hefei, 230088, China
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2
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Zerba C, Kuhlenkamp C, Imamoğlu A, Knap M. Realizing Topological Superconductivity in Tunable Bose-Fermi Mixtures with Transition Metal Dichalcogenide Heterostructures. PHYSICAL REVIEW LETTERS 2024; 133:056902. [PMID: 39159121 DOI: 10.1103/physrevlett.133.056902] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/16/2023] [Accepted: 06/21/2024] [Indexed: 08/21/2024]
Abstract
Heterostructures of two-dimensional transition metal dichalcogenides are emerging as a promising platform for investigating exotic correlated states of matter. Here, we propose to engineer Bose-Fermi mixtures in these systems by coupling interlayer excitons to doped charges in a trilayer structure. Their interactions are determined by the interlayer trion, whose spin-selective nature allows excitons to mediate an attractive interaction between charge carriers of only one spin species. Remarkably, we find that this causes the system to become unstable to topological p+ip superconductivity at low temperatures. We then demonstrate a general mechanism to develop and control this unconventional state by tuning the trion binding energy using a solid-state Feshbach resonance.
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Affiliation(s)
| | - Clemens Kuhlenkamp
- Technical University of Munich, TUM School of Natural Sciences, Physics Department, 85748 Garching, Germany
- Munich Center for Quantum Science and Technology (MCQST), Schellingstrasse 4, 80799 München, Germany
- Institute for Quantum Electronics, ETH Zürich, CH-8093 Zürich, Switzerland
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3
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Shkvarina EG, Postnikov MS, Merentsov AI, Shkvarin AS, Radzivonchik DI, Gigli L, Gaboardi M, Plaisier JR, Titov AN. Transformation of the crystal structure of Ni 0.5TiSe 2 under in situ heating. Phys Chem Chem Phys 2024; 26:15999-16007. [PMID: 38775094 DOI: 10.1039/d4cp00453a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2024]
Abstract
The crystal structure of the Ni0.5TiSe2 compound has been studied in situ in the temperature range of 25-1000 °C using synchrotron radiation X-ray diffraction. The previously known order-disorder transition in the Ni sublattice at ∼100 °C was found to be a second-order phase transition and belongs to the 3D Ising universality class. Reversible extraction of nickel selenides was observed in the temperature range of 275-975 °C. It was explained in terms of Ni extraction from Ni0.5TiSe2 due to the thermal widening of the Ni 3d/Ti 3d/Se 4p impurity band. The Ni-TiSe2 phase diagram follows the typical pattern of MxTiSe2 (M - transition metal) compounds.
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Affiliation(s)
- E G Shkvarina
- M.N. Miheev Institute of Metal Physics of Ural Branch of Russian Academy of Sciences, 620990, Ekaterinburg, Russia.
| | - M S Postnikov
- M.N. Miheev Institute of Metal Physics of Ural Branch of Russian Academy of Sciences, 620990, Ekaterinburg, Russia.
| | - A I Merentsov
- M.N. Miheev Institute of Metal Physics of Ural Branch of Russian Academy of Sciences, 620990, Ekaterinburg, Russia.
| | - A S Shkvarin
- M.N. Miheev Institute of Metal Physics of Ural Branch of Russian Academy of Sciences, 620990, Ekaterinburg, Russia.
| | - D I Radzivonchik
- M.N. Miheev Institute of Metal Physics of Ural Branch of Russian Academy of Sciences, 620990, Ekaterinburg, Russia.
| | - L Gigli
- Elettra-Sincrotrone Trieste S.C.p.A, S.S. 14, km 163.5, 34149, Basovizza, TS, Italy
| | - M Gaboardi
- Elettra-Sincrotrone Trieste S.C.p.A, S.S. 14, km 163.5, 34149, Basovizza, TS, Italy
| | - J R Plaisier
- Elettra-Sincrotrone Trieste S.C.p.A, S.S. 14, km 163.5, 34149, Basovizza, TS, Italy
| | - A N Titov
- M.N. Miheev Institute of Metal Physics of Ural Branch of Russian Academy of Sciences, 620990, Ekaterinburg, Russia.
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4
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Zhou H, Liang K, Bi L, Shi Y, Wang Z, Li S. Spotlight: Visualization of Moiré Quantum Phenomena in Transition Metal Dichalcogenide with Scanning Tunneling Microscopy. ACS APPLIED ELECTRONIC MATERIALS 2024; 6:1530-1541. [PMID: 38558951 PMCID: PMC10976882 DOI: 10.1021/acsaelm.3c01328] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/21/2023] [Revised: 01/09/2024] [Accepted: 01/10/2024] [Indexed: 04/04/2024]
Abstract
Transition metal dichalcogenide (TMD) moiré superlattices have emerged as a significant area of study in condensed matter physics. Thanks to their superior optical properties, tunable electronic band structure, strong Coulomb interactions, and quenched electron kinetic energy, they offer exciting avenues to explore correlated quantum phenomena, topological properties, and light-matter interactions. In recent years, scanning tunneling microscopy (STM) has made significant impacts on the study of these fields by enabling intrinsic surface visualization and spectroscopic measurements with unprecedented atomic scale detail. Here, we spotlight the key findings and innovative developments in imaging and characterization of TMD heterostructures via STM, from its initial implementation on the in situ grown sample to the latest photocurrent tunneling microscopy. The evolution in sample design, progressing from a conductive to an insulating substrate, has not only expanded our control over TMD moiré superlattices but also promoted an understanding of their structures and strongly correlated properties, such as the structural reconstruction and formation of generalized two-dimensional Wigner crystal states. In addition to highlighting recent advancements, we outline upcoming challenges, suggest the direction of future research, and advocate for the versatile use of STM to further comprehend and manipulate the quantum dynamics in TMD moiré superlattices.
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Affiliation(s)
- Hao Zhou
- Department
of Chemistry and Biochemistry, University
of California, San Diego, La Jolla, California 92093-0309, United States
- Program
in Materials Science and Engineering, University
of California, San Diego, La Jolla, California 92093-0418, United States
| | - Kangkai Liang
- Department
of Chemistry and Biochemistry, University
of California, San Diego, La Jolla, California 92093-0309, United States
- Program
in Materials Science and Engineering, University
of California, San Diego, La Jolla, California 92093-0418, United States
| | - Liya Bi
- Department
of Chemistry and Biochemistry, University
of California, San Diego, La Jolla, California 92093-0309, United States
- Program
in Materials Science and Engineering, University
of California, San Diego, La Jolla, California 92093-0418, United States
| | - Yueqing Shi
- Department
of Chemistry and Biochemistry, University
of California, San Diego, La Jolla, California 92093-0309, United States
| | - Zihao Wang
- Department
of Chemistry and Biochemistry, University
of California, San Diego, La Jolla, California 92093-0309, United States
- School
of Physics, Nankai University, Tianjin 300071, China
| | - Shaowei Li
- Department
of Chemistry and Biochemistry, University
of California, San Diego, La Jolla, California 92093-0309, United States
- Program
in Materials Science and Engineering, University
of California, San Diego, La Jolla, California 92093-0418, United States
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Jamwal P, Ahuja R, Kumar R. Van Hove singularity driven enhancement of superconductivity in two-dimensional tungsten monofluoride (WF). JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2024; 36:245001. [PMID: 38411011 DOI: 10.1088/1361-648x/ad2d47] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/09/2024] [Accepted: 02/26/2024] [Indexed: 02/28/2024]
Abstract
Superconductivity in two-dimensional materials has gained significant attention in the last few years. In this work, we report phonon-mediated superconductivity investigations in monolayer Tungsten monofluoride (WF) by solving anisotropic Migdal Eliashberg equations as implemented in EPW. By employing first-principles calculations, our examination of phonon dispersion spectra suggests that WF is dynamically stable. Our results show that WF has weak electron-phonon coupling (EPC) strength (λ) of 0.49 with superconducting transition temperature (Tc) of 2.6 K. A saddle point is observed at 0.11 eV below the Fermi level (EF) of WF, which corresponds to the Van Hove singularity (VHS). On shifting the Fermi level to the VHS by hole doping (3.7 × 1014cm-2), the EPC strength increases to 0.93, which leads to an increase in theTcto 11 K. However, the superconducting transition temperature of both pristine and doped WF increases to approximately 7.2 K and 17.2 K, respectively, by applying the Full Bandwidth (FBW) anisotropic Migdal-Eliashberg equations. Our results provide a platform for the experimental realization of superconductivity in WF and enhancement of the superconducting transition temperature by adjusting the position ofEFto the VHS.
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Affiliation(s)
- Prarena Jamwal
- Department of Physics, Indian Institute of Technology Ropar, Rupnagar 140001, Punjab, India
| | - Rajeev Ahuja
- Department of Physics, Indian Institute of Technology Ropar, Rupnagar 140001, Punjab, India
- Condensed Matter Theory Group, Department of Physics and Astronomy, Uppsala University, Box 516, Uppsala 75120, Sweden
| | - Rakesh Kumar
- Department of Physics, Indian Institute of Technology Ropar, Rupnagar 140001, Punjab, India
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6
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Shkvarin A, Merentsov A, Postnikov M, Shkvarina E, Volegov A, Pryanichnikov S, Zayats P, Lebedev A, Chumakov R, Titov A. Electronic and Crystal Structure of New Cr xZrSe 2 Intercalation Compounds. Inorg Chem 2024; 63:934-946. [PMID: 38175815 DOI: 10.1021/acs.inorgchem.3c02114] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2024]
Abstract
New intercalation compounds CrxZrSe2 were synthesized and thoroughly studied. Cr atoms were found to occupy the positions both tetrahedrally and octahedrally coordinated by the Se atoms in the interlayer gap. The magnetic properties and electrical resistivity were studied in the temperature ranges of 2.4-300 K and 80-340 K, respectively. The compounds change their behavior from semiconducting (x = 0.1) to metallic (x > 0.1). The magnetic interaction strongly depends on the Cr content and temperature. The spin-glass state with antiferromagnetic interaction exists at T < Tcrit for CrxZrSe2 with x ≤ 0.2, while at x ≥ 0.3 ferromagnetic contribution arises as well. The single crystals of CrxZrSe2 were grown to study the electronic structure of the materials. A combination of the X-ray photoelectron spectroscopy (including that across Cr 2p-3d and Zr 3p-4d resonance) and X-ray absorption spectroscopy methods allowed to propose the location of the Cr 3d-states in the Se 3p-Zr 4d energy gap.
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Affiliation(s)
- Alexey Shkvarin
- M.N. Mikheev lnstitute of Metal Physics, Ural Branch of Russian Academy of Sciences, 620137 Ekaterinburg, Russia
| | - Alexander Merentsov
- M.N. Mikheev lnstitute of Metal Physics, Ural Branch of Russian Academy of Sciences, 620137 Ekaterinburg, Russia
| | - Mikhail Postnikov
- M.N. Mikheev lnstitute of Metal Physics, Ural Branch of Russian Academy of Sciences, 620137 Ekaterinburg, Russia
| | - Elena Shkvarina
- M.N. Mikheev lnstitute of Metal Physics, Ural Branch of Russian Academy of Sciences, 620137 Ekaterinburg, Russia
| | - Aleksey Volegov
- M.N. Mikheev lnstitute of Metal Physics, Ural Branch of Russian Academy of Sciences, 620137 Ekaterinburg, Russia
- Ural Federal University, Institute of Natural Sciences and Mathematics, 620002 Ekaterinburg, Russia
| | - Stepan Pryanichnikov
- Institute of Metallurgy, Ural Branch of Russian Academy of Sciences, 620016 Ekaterinburg, Russia
| | - Polina Zayats
- M.N. Mikheev lnstitute of Metal Physics, Ural Branch of Russian Academy of Sciences, 620137 Ekaterinburg, Russia
| | - Alexey Lebedev
- National Research Centre "Kurchatov Institute", 1 Akademika Kurchatova pl., 123182 Moscow, Russia
| | - Ratibor Chumakov
- National Research Centre "Kurchatov Institute", 1 Akademika Kurchatova pl., 123182 Moscow, Russia
| | - Alexander Titov
- M.N. Mikheev lnstitute of Metal Physics, Ural Branch of Russian Academy of Sciences, 620137 Ekaterinburg, Russia
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7
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Zhu S, Wu J, Zhu P, Pei C, Wang Q, Jia D, Wang X, Zhao Y, Gao L, Li C, Cao W, Zhang M, Zhang L, Li M, Gou H, Yang W, Sun J, Chen Y, Wang Z, Yao Y, Qi Y. Pressure-Induced Superconductivity and Topological Quantum Phase Transitions in the Topological Semimetal ZrTe 2. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2023; 10:e2301332. [PMID: 37944509 PMCID: PMC10724415 DOI: 10.1002/advs.202301332] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2023] [Revised: 09/04/2023] [Indexed: 11/12/2023]
Abstract
Topological transition metal dichalcogenides (TMDCs) have attracted much attention due to their potential applications in spintronics and quantum computations. In this work, the structural and electronic properties of topological TMDCs candidate ZrTe2 are systematically investigated under high pressure. A pressure-induced Lifshitz transition is evidenced by the change of charge carrier type as well as the Fermi surface. Superconductivity is observed at around 8.3 GPa without structural phase transition. A typical dome-shape phase diagram is obtained with the maximum Tc of 5.6 K for ZrTe2 . Furthermore, the theoretical calculations suggest the presence of multiple pressure-induced topological quantum phase transitions, which coexists with emergence of superconductivity. The results demonstrate that ZrTe2 with nontrivial topology of electronic states displays new ground states upon compression.
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Affiliation(s)
- Shihao Zhu
- School of Physical Science and TechnologyShanghaiTech UniversityShanghai201210China
| | - Juefei Wu
- School of Physical Science and TechnologyShanghaiTech UniversityShanghai201210China
| | - Peng Zhu
- Centre for Quantum PhysicsKey Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement (MOE)School of PhysicsBeijing Institute of TechnologyBeijing100081China
- Beijing Key Lab of Nanophotonics and Ultrafine Optoelectronic SystemsBeijing Institute of TechnologyBeijing100081China
- Material Science CenterYangtze Delta Region Academy of Beijing Institute of TechnologyJiaxing314011China
| | - Cuiying Pei
- School of Physical Science and TechnologyShanghaiTech UniversityShanghai201210China
| | - Qi Wang
- School of Physical Science and TechnologyShanghaiTech UniversityShanghai201210China
- ShanghaiTech Laboratory for Topological PhysicsShanghaiTech UniversityShanghai201210China
| | - Donghan Jia
- Center for High Pressure Science and Technology Advanced ResearchShanghai201203China
| | - Xinyu Wang
- Center for High Pressure Science and Technology Advanced ResearchShanghai201203China
| | - Yi Zhao
- School of Physical Science and TechnologyShanghaiTech UniversityShanghai201210China
| | - Lingling Gao
- School of Physical Science and TechnologyShanghaiTech UniversityShanghai201210China
| | - Changhua Li
- School of Physical Science and TechnologyShanghaiTech UniversityShanghai201210China
| | - Weizheng Cao
- School of Physical Science and TechnologyShanghaiTech UniversityShanghai201210China
| | - Mingxin Zhang
- School of Physical Science and TechnologyShanghaiTech UniversityShanghai201210China
| | - Lili Zhang
- Shanghai Synchrotron Radiation FacilityShanghai Advanced Research InstituteChinese Academy of SciencesShanghai201203China
| | - Mingtao Li
- Center for High Pressure Science and Technology Advanced ResearchShanghai201203China
| | - Huiyang Gou
- Center for High Pressure Science and Technology Advanced ResearchShanghai201203China
| | - Wenge Yang
- Center for High Pressure Science and Technology Advanced ResearchShanghai201203China
| | - Jian Sun
- National Laboratory of Solid State MicrostructuresSchool of Physics and Collaborative Innovation Center of Advanced MicrostructuresNanjing UniversityNanjing210093China
| | - Yulin Chen
- School of Physical Science and TechnologyShanghaiTech UniversityShanghai201210China
- ShanghaiTech Laboratory for Topological PhysicsShanghaiTech UniversityShanghai201210China
- Department of PhysicsClarendon LaboratoryUniversity of OxfordParks RoadOxfordOX1 3PUUK
| | - Zhiwei Wang
- Centre for Quantum PhysicsKey Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement (MOE)School of PhysicsBeijing Institute of TechnologyBeijing100081China
- Beijing Key Lab of Nanophotonics and Ultrafine Optoelectronic SystemsBeijing Institute of TechnologyBeijing100081China
- Material Science CenterYangtze Delta Region Academy of Beijing Institute of TechnologyJiaxing314011China
| | - Yugui Yao
- Centre for Quantum PhysicsKey Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement (MOE)School of PhysicsBeijing Institute of TechnologyBeijing100081China
- Beijing Key Lab of Nanophotonics and Ultrafine Optoelectronic SystemsBeijing Institute of TechnologyBeijing100081China
| | - Yanpeng Qi
- School of Physical Science and TechnologyShanghaiTech UniversityShanghai201210China
- ShanghaiTech Laboratory for Topological PhysicsShanghaiTech UniversityShanghai201210China
- Shanghai Key Laboratory of High‐resolution Electron MicroscopyShanghaiTech UniversityShanghai201210China
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8
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Gerber E, Torrisi SB, Shabani S, Seewald E, Pack J, Hoffman JE, Dean CR, Pasupathy AN, Kim EA. High-throughput ab initio design of atomic interfaces using InterMatch. Nat Commun 2023; 14:7921. [PMID: 38040714 PMCID: PMC10692083 DOI: 10.1038/s41467-023-43496-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2023] [Accepted: 11/10/2023] [Indexed: 12/03/2023] Open
Abstract
Forming a hetero-interface is a materials-design strategy that can access an astronomically large phase space. However, the immense phase space necessitates a high-throughput approach for an optimal interface design. Here we introduce a high-throughput computational framework, InterMatch, for efficiently predicting charge transfer, strain, and superlattice structure of an interface by leveraging the databases of individual bulk materials. Specifically, the algorithm reads in the lattice vectors, density of states, and the stiffness tensors for each material in their isolated form from the Materials Project. From these bulk properties, InterMatch estimates the interfacial properties. We benchmark InterMatch predictions for the charge transfer against experimental measurements and supercell density-functional theory calculations. We then use InterMatch to predict promising interface candidates for doping transition metal dichalcogenide MoSe2. Finally, we explain experimental observation of factor of 10 variation in the supercell periodicity within a few microns in graphene/α-RuCl3 by exploring low energy superlattice structures as a function of twist angle using InterMatch. We anticipate our open-source InterMatch algorithm accelerating and guiding ever-growing interfacial design efforts. Moreover, the interface database resulting from the InterMatch searches presented in this paper can be readily accessed online.
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Affiliation(s)
- Eli Gerber
- School of Applied and Engineering Physics, Cornell University, Ithaca, NY, 14853, USA.
| | - Steven B Torrisi
- Department of Physics, Harvard University, Cambridge, MA, 02138, USA
- Energy & Materials Division, Toyota Research Institute, Los Altos, CA, 94022, USA
| | - Sara Shabani
- Department of Physics, Columbia University, New York, NY, USA
| | - Eric Seewald
- Department of Physics, Columbia University, New York, NY, USA
| | - Jordan Pack
- Department of Physics, Columbia University, New York, NY, USA
| | - Jennifer E Hoffman
- Department of Physics, Harvard University, Cambridge, MA, 02138, USA
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, 02138, USA
| | - Cory R Dean
- Department of Physics, Columbia University, New York, NY, USA
| | | | - Eun-Ah Kim
- Department of Physics, Cornell University, Ithaca, NY, 14853, USA
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9
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Xie YM, Law KT. Orbital Fulde-Ferrell Pairing State in Moiré Ising Superconductors. PHYSICAL REVIEW LETTERS 2023; 131:016001. [PMID: 37478419 DOI: 10.1103/physrevlett.131.016001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/27/2023] [Accepted: 06/09/2023] [Indexed: 07/23/2023]
Abstract
In this Letter, we study superconducting moiré homobilayer transition metal dichalcogenides where the Ising spin-orbit coupling (SOC) is much larger than the moiré bandwidth. We call such noncentrosymmetric superconductors, moiré Ising superconductors. Because of the large Ising SOC, the depairing effect caused by the Zeeman field is negligible and the in-plane upper critical field (B_{c2}) is determined by the orbital effects. This allows us to study the effect of large orbital fields. Interestingly, when the applied in-plane field is larger than the conventional orbital B_{c2}, a finite-momentum pairing phase would appear which we call the orbital Fulde-Ferrell (FF) state. In this state, the Cooper pairs acquire a net momentum of 2q_{B}, where 2q_{B}=eBd is the momentum shift caused by the magnetic field B and d denotes the layer separation. This orbital field-driven FF state is different from the conventional FF state driven by Zeeman effects in Rashba superconductors. Remarkably, we predict that the FF pairing would result in a giant superconducting diode effect under electric gating when layer asymmetry is induced. An upturn of the B_{c2} as the temperature is lowered, coupled with the giant superconducting diode effect, would allow the detection of the orbital FF state.
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Affiliation(s)
- Ying-Ming Xie
- Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China
| | - K T Law
- Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China
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10
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Salimon IA, Zharkova EV, Averchenko AV, Kumar J, Somov P, Abbas OA, Lagoudakis PG, Mailis S. Laser-Synthesized 2D-MoS 2 Nanostructured Photoconductors. MICROMACHINES 2023; 14:mi14051036. [PMID: 37241659 DOI: 10.3390/mi14051036] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/25/2023] [Revised: 05/08/2023] [Accepted: 05/09/2023] [Indexed: 05/28/2023]
Abstract
The direct laser synthesis of periodically nanostructured 2D transition metal dichalcogenide (2D-TMD) films, from single source precursors, is presented here. Laser synthesis of MoS2 and WS2 tracks is achieved by localized thermal dissociation of Mo and W thiosalts, caused by the strong absorption of continuous wave (c.w.) visible laser radiation by the precursor film. Moreover, within a range of irradiation conditions we have observed occurrence of 1D and 2D spontaneous periodic modulation in the thickness of the laser-synthesized TMD films, which in some cases is so extreme that it results in the formation of isolated nanoribbons with a width of ~200 nm and a length of several micrometers. The formation of these nanostructures is attributed to the effect that is known as laser-induced periodic surface structures (LIPSS), which is caused by self-organized modulation of the incident laser intensity distribution due to optical feedback from surface roughness. We have fabricated two terminal photoconductive detectors based on nanostructured and continuous films and we show that the nanostructured TMD films exhibit enhanced photo-response, with photocurrent yield increased by three orders of magnitude as compared to their continuous counterparts.
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Affiliation(s)
- Igor A Salimon
- Center for Photonic Science and Engineering (CPhSE), Skolkovo Institute of Science and Technology, 3 Nobel Street, 143026 Moscow, Russia
| | - Ekaterina V Zharkova
- Center for Photonic Science and Engineering (CPhSE), Skolkovo Institute of Science and Technology, 3 Nobel Street, 143026 Moscow, Russia
| | - Aleksandr V Averchenko
- Center for Photonic Science and Engineering (CPhSE), Skolkovo Institute of Science and Technology, 3 Nobel Street, 143026 Moscow, Russia
| | - Jatin Kumar
- Center for Photonic Science and Engineering (CPhSE), Skolkovo Institute of Science and Technology, 3 Nobel Street, 143026 Moscow, Russia
| | - Pavel Somov
- Center for Energy Science and Technology (CEST), Skolkovo Institute of Science and Technology, 3 Nobel Street, 143026 Moscow, Russia
| | - Omar A Abbas
- Center for Photonic Science and Engineering (CPhSE), Skolkovo Institute of Science and Technology, 3 Nobel Street, 143026 Moscow, Russia
| | - Pavlos G Lagoudakis
- Center for Photonic Science and Engineering (CPhSE), Skolkovo Institute of Science and Technology, 3 Nobel Street, 143026 Moscow, Russia
| | - Sakellaris Mailis
- Center for Photonic Science and Engineering (CPhSE), Skolkovo Institute of Science and Technology, 3 Nobel Street, 143026 Moscow, Russia
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11
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Jarjour A, Ferguson GM, Schaefer BT, Lee M, Loh YL, Trivedi N, Nowack KC. Superfluid response of an atomically thin gate-tuned van der Waals superconductor. Nat Commun 2023; 14:2055. [PMID: 37045826 PMCID: PMC10097715 DOI: 10.1038/s41467-023-37210-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2022] [Accepted: 03/03/2023] [Indexed: 04/14/2023] Open
Abstract
A growing number of two-dimensional superconductors are being discovered in the family of exfoliated van der Waals materials. Due to small sample volume, the superfluid response of these materials has not been characterized. Here, we use a local magnetic probe to directly measure this key property of the tunable, gate-induced superconducting state in MoS2. We find that the backgate changes the transition temperature non-monotonically whereas the superfluid stiffness at low temperature and the normal state conductivity monotonically increase. In some devices, we find direct signatures in agreement with a Berezinskii-Kosterlitz-Thouless transition, whereas in others we find a broadened onset of the superfluid response. We show that the observed behavior is consistent with disorder playing an important role in determining the properties of superconducting MoS2. Our work demonstrates that magnetic property measurements are within reach for superconducting devices based on exfoliated sheets and reveals that the superfluid response significantly deviates from simple BCS-like behavior.
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Affiliation(s)
- Alexander Jarjour
- Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, NY, USA
| | - G M Ferguson
- Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, NY, USA
| | - Brian T Schaefer
- Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, NY, USA
| | - Menyoung Lee
- Kavli Institute at Cornell for Nanoscale Science, Ithaca, NY, USA
- School of Electrical and Computer Engineering, Cornell University, Ithaca, NY, USA
| | - Yen Lee Loh
- Department of Physics and Astrophysics, University of North Dakota, Grand Forks, ND, USA
| | - Nandini Trivedi
- Department of Physics, The Ohio State University, Columbus, OH, USA
| | - Katja C Nowack
- Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, NY, USA.
- Kavli Institute at Cornell for Nanoscale Science, Ithaca, NY, USA.
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12
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Wu YM, Wu Z, Yao H. Pair-Density-Wave and Chiral Superconductivity in Twisted Bilayer Transition Metal Dichalcogenides. PHYSICAL REVIEW LETTERS 2023; 130:126001. [PMID: 37027848 DOI: 10.1103/physrevlett.130.126001] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/18/2022] [Accepted: 02/24/2023] [Indexed: 06/19/2023]
Abstract
We theoretically explore possible orders induced by weak repulsive interactions in twisted bilayer transition metal dichalcogenides (e.g., WSe_{2}) in the presence of an out-of-plane electric field. Using renormalization group analysis, we show that superconductivity survives even with the conventional van Hove singularities. We find that topological chiral superconducting states with Chern number N=1, 2, 4 (namely, p+ip, d+id, and g+ig) appear over a large parameter region with a moiré filling factor around n=1. At some special values of applied electric field and in the presence of a weak out-of-plane Zeeman field, spin-polarized pair-density-wave (PDW) superconductivity can emerge. This spin-polarized PDW state can be probed by experiments such as spin-polarized STM measuring spin-resolved pairing gap and quasiparticle interference. Moreover, the spin-polarized PDW could lead to a spin-polarized superconducting diode effect.
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Affiliation(s)
- Yi-Ming Wu
- Institute for Advanced Study, Tsinghua University, Beijing 100084, China
- Stanford Institute for Theoretical Physics, Stanford University, Stanford, California 94305, USA
| | - Zhengzhi Wu
- Institute for Advanced Study, Tsinghua University, Beijing 100084, China
| | - Hong Yao
- Institute for Advanced Study, Tsinghua University, Beijing 100084, China
- State Key Laboratory of Low Dimensional Quantum Physics, Tsinghua University, Beijing 100084, China
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13
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Correa L, Ferreira PP, de Faria LR, Fim VM, da Luz MS, Torikachvili MS, Heil C, Eleno LTF, Machado AJS. Superconductivity in Te-Deficient ZrTe 2. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2023; 127:5162-5168. [PMID: 36960103 PMCID: PMC10026068 DOI: 10.1021/acs.jpcc.2c08836] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/17/2022] [Revised: 02/27/2023] [Indexed: 06/18/2023]
Abstract
We present structural, electrical, and thermoelectric potential measurements on high-quality single crystals of ZrTe1.8 grown from isothermal chemical vapor transport. These measurements show that the Te-deficient ZrTe1.8, which forms the same structure as the nonsuperconducting ZrTe2, is superconducting below 3.2 K. The temperature dependence of the upper critical field (H c2) deviates from the behavior expected in conventional single-band superconductors, being best described by an electron-phonon two-gap superconducting model with strong intraband coupling. For the ZrTe1.8 single crystals, the Seebeck potential measurements suggest that the charge carriers are predominantly negative, in agreement with the ab initio calculations. Through first-principles calculations within DFT, we show that the slight reduction of Te occupancy in ZrTe2 unexpectedly gives origin to density of states peaks at the Fermi level due to the formation of localized Zr-d bands, possibly promoting electronic instabilities at the Fermi level and an increase at the critical temperature according to the standard BCS theory. These findings highlight that the Te deficiency promotes the electronic conditions for the stability of the superconducting ground state, suggesting that defects can fine-tune the electronic structure to support superconductivity.
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Affiliation(s)
- Lucas
E. Correa
- Universidade
de São Paulo, Escola de Engenharia
de Lorena, DEMAR, 12612-550 Lorena, Brazil
| | - Pedro P. Ferreira
- Universidade
de São Paulo, Escola de Engenharia
de Lorena, DEMAR, 12612-550 Lorena, Brazil
- Institute
of Theoretical and Computational Physics, Graz University of Technology, NAWI Graz, 8010 Graz, Austria
| | - Leandro R. de Faria
- Universidade
de São Paulo, Escola de Engenharia
de Lorena, DEMAR, 12612-550 Lorena, Brazil
| | - Vitor M. Fim
- Universidade
de São Paulo, Escola de Engenharia
de Lorena, DEMAR, 12612-550 Lorena, Brazil
| | - Mario S. da Luz
- Instituto
de Ciências Tecnológicas e Exatas, Universidade Federal do Triângulo Mineiro, 38025-180 Uberaba, Minas Gerais, Brazil
| | - Milton S. Torikachvili
- Department
of Physics, San Diego State University, San Diego, California 92182-1233, United States
| | - Christoph Heil
- Institute
of Theoretical and Computational Physics, Graz University of Technology, NAWI Graz, 8010 Graz, Austria
| | - Luiz T. F. Eleno
- Universidade
de São Paulo, Escola de Engenharia
de Lorena, DEMAR, 12612-550 Lorena, Brazil
| | - Antonio J. S. Machado
- Universidade
de São Paulo, Escola de Engenharia
de Lorena, DEMAR, 12612-550 Lorena, Brazil
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14
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Li YX, Yao ZJ, Yu SL, Li JX. Superconductivity and density-wave fluctuations in an extended triangular Hubbard model: an application to SnSe 2. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2022; 35:045602. [PMID: 36541553 DOI: 10.1088/1361-648x/aca85e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/24/2022] [Accepted: 12/01/2022] [Indexed: 06/17/2023]
Abstract
We employ the fluctuation-exchange approximation to study the relation of superconducting pairing symmetries and density-wave fluctuations based on the extended triangular Hubbard model upon electron doping and interactions, with an possible application to the layered metal dichalcogenide SnSe2. For the case where the interactions between electrons contain only the on-site Hubbard term, the superconducting pairings are mainly mediated by spin fluctuations, and the spin-singlet pairing with thed-wave symmetry robustly dominates in the low and moderate doping levels, and ad-wave to extendeds-wave transition is observed as the electron doping reachesn = 1. When the near-neighbor site Coulomb interactions are also included, the charge fluctuations are enhanced, and the spin-triplet pairings with thep-wave andf-wave symmetries can be realized in the high and low doping levels, respectively.
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Affiliation(s)
- Yun-Xiao Li
- National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093, People's Republic of China
| | - Zi-Jian Yao
- Department of Physics, Nanjing Normal University, Nanjing 210023, People's Republic of China
| | - Shun-Li Yu
- National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093, People's Republic of China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, People's Republic of China
| | - Jian-Xin Li
- National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093, People's Republic of China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, People's Republic of China
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15
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Yi H, Hu LH, Wang Y, Xiao R, Cai J, Hickey DR, Dong C, Zhao YF, Zhou LJ, Zhang R, Richardella AR, Alem N, Robinson JA, Chan MHW, Xu X, Samarth N, Liu CX, Chang CZ. Crossover from Ising- to Rashba-type superconductivity in epitaxial Bi 2Se 3/monolayer NbSe 2 heterostructures. NATURE MATERIALS 2022; 21:1366-1372. [PMID: 36302957 DOI: 10.1038/s41563-022-01386-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/11/2022] [Accepted: 09/21/2022] [Indexed: 06/16/2023]
Abstract
A topological insulator (TI) interfaced with an s-wave superconductor has been predicted to host topological superconductivity. Although the growth of epitaxial TI films on s-wave superconductors has been achieved by molecular-beam epitaxy, it remains an outstanding challenge for synthesizing atomically thin TI/superconductor heterostructures, which are critical for engineering the topological superconducting phase. Here we used molecular-beam epitaxy to grow Bi2Se3 films with a controlled thickness on monolayer NbSe2 and performed in situ angle-resolved photoemission spectroscopy and ex situ magnetotransport measurements on these heterostructures. We found that the emergence of Rashba-type bulk quantum-well bands and spin-non-degenerate surface states coincides with a marked suppression of the in-plane upper critical magnetic field of the superconductivity in Bi2Se3/monolayer NbSe2 heterostructures. This is a signature of a crossover from Ising- to Rashba-type superconducting pairings, induced by altering the Bi2Se3 film thickness. Our work opens a route for exploring a robust topological superconducting phase in TI/Ising superconductor heterostructures.
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Affiliation(s)
- Hemian Yi
- Department of Physics, The Pennsylvania State University, University Park, PA, USA
| | - Lun-Hui Hu
- Department of Physics, The Pennsylvania State University, University Park, PA, USA
| | - Yuanxi Wang
- Department of Physics, The Pennsylvania State University, University Park, PA, USA
- Department of Physics, University of North Texas, Denton, TX, USA
| | - Run Xiao
- Department of Physics, The Pennsylvania State University, University Park, PA, USA
| | - Jiaqi Cai
- Department of Physics, University of Washington, Seattle, WA, USA
| | - Danielle Reifsnyder Hickey
- Department of Chemistry, The Pennsylvania State University, University Park, PA, USA
- Department of Materials Science and Engineering, The Pennsylvania State University, University Park, PA, USA
| | - Chengye Dong
- Department of Materials Science and Engineering, The Pennsylvania State University, University Park, PA, USA
| | - Yi-Fan Zhao
- Department of Physics, The Pennsylvania State University, University Park, PA, USA
| | - Ling-Jie Zhou
- Department of Physics, The Pennsylvania State University, University Park, PA, USA
| | - Ruoxi Zhang
- Department of Physics, The Pennsylvania State University, University Park, PA, USA
| | | | - Nasim Alem
- Department of Materials Science and Engineering, The Pennsylvania State University, University Park, PA, USA
| | - Joshua A Robinson
- Department of Materials Science and Engineering, The Pennsylvania State University, University Park, PA, USA
| | - Moses H W Chan
- Department of Physics, The Pennsylvania State University, University Park, PA, USA
| | - Xiaodong Xu
- Department of Physics, University of Washington, Seattle, WA, USA
- Department of Materials Science and Engineering, University of Washington, Seattle, WA, USA
| | - Nitin Samarth
- Department of Physics, The Pennsylvania State University, University Park, PA, USA
| | - Chao-Xing Liu
- Department of Physics, The Pennsylvania State University, University Park, PA, USA
| | - Cui-Zu Chang
- Department of Physics, The Pennsylvania State University, University Park, PA, USA.
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16
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Ding D, Qu Z, Han X, Han C, Zhuang Q, Yu XL, Niu R, Wang Z, Li Z, Gan Z, Wu J, Lu J. Multivalley Superconductivity in Monolayer Transition Metal Dichalcogenides. NANO LETTERS 2022; 22:7919-7926. [PMID: 36173038 DOI: 10.1021/acs.nanolett.2c02947] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
In transition metal dichalcogenides (TMDs), Ising superconductivity with an antisymmetric spin texture on the Fermi surface has attracted wide interest due to the exotic pairing and topological properties. However, it is not clear whether the Q valley with a giant spin splitting is involved in the superconductivity of heavily doped semiconducting 2H-TMDs. Here by taking advantage of a high-quality monolayer WS2 on hexagonal boron nitride flakes, we report an ionic-gating induced superconducting dome with a record high critical temperature of ∼6 K, accompanied by an emergent nonlinear Hall effect. The nonlinearity indicates the development of an additional high-mobility channel, which (corroborated by first principle calculations) can be ascribed to the population of Q valleys. Thus, multivalley population at K and Q is suggested to be a prerequisite for developing superconductivity. The involvement of Q valleys also provides insights to the spin textured Fermi surface of Ising superconductivity in the large family of transition metal dichalcogenides.
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Affiliation(s)
- Dongdong Ding
- State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, China
| | - Zhuangzhuang Qu
- State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, China
| | - Xiangyan Han
- State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, China
| | - Chunrui Han
- Institute of Microelectronics, Chinese Academy of Sciences, Beijing 100029, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Quan Zhuang
- Shenzhen Institute for Quantum Science and Engineering (SIQSE), Southern University of Science and Technology, Shenzhen 518055, China
- Inner Mongolia Key Laboratory of Carbon Nanomaterials, Nano Innovation Institute (NII), Inner Mongolia Minzu University, Tongliao 028000, China
| | - Xiang-Long Yu
- Shenzhen Institute for Quantum Science and Engineering (SIQSE), Southern University of Science and Technology, Shenzhen 518055, China
- International Quantum Academy, Shenzhen 518048, China
| | - Ruirui Niu
- State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, China
| | - Zhiyu Wang
- State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, China
| | - Zhuoxian Li
- State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, China
| | - Zizhao Gan
- State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, China
| | - Jiansheng Wu
- Shenzhen Institute for Quantum Science and Engineering (SIQSE), Southern University of Science and Technology, Shenzhen 518055, China
- International Quantum Academy, Shenzhen 518048, China
| | - Jianming Lu
- State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, China
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17
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Gavryushkin P, Sagatov N, Sukhanova E, Medrish I, Popov Z. Janus structures of SMoSe and SVSe compositions with low enthalpy and unusual crystal chemistry. J Appl Crystallogr 2022. [DOI: 10.1107/s1600576722008202] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
The recent synthesis of single-layer Janus-type transition metal dichalcogenides (TMDs) raises the question of the existence of other possible 2D structures with an asymmetric out-of-plane structural configuration. In the present work, a theoretical search for new Janus structures having SMoSe and SVSe compositions is performed. A detailed crystal-chemical analysis of the predicted structures is carried out, and it is shown that some of the dynamically stable structures are characterized by crystal-chemical features that are unique among TMDs, including quadruple Mo—Mo bonds and covalent S—S and Se—Se bonds. It is also shown that Mo-bearing TMDs have a tendency to form strong Mo—Mo bonds with chains or isolated dimers of molybdenum atoms, while in the case of vanadium-containing TMDs this feature is not characteristic. Two predicted crystal structures, called 1M-SVSe and 1A′-SMoSe, are especially promising for experimental synthesis and practical applications owing to their dynamical stability and rather low value of enthalpy compared with known structures. The enthalpy of 1M-SVSe is 0.22 eV per formula unit lower than that of 1T-SVSe, while the enthalpy of 1A′-SMoSe is 0.12 eV per formula unit lower than the enthalpy of 1T-SMoSe. The performed topological analysis showed that the predicted structures are unique and do not have analogues in the Inorganic Crystal Structure Database.
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18
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Ramires A. Nonunitary superconductivity in complex quantum materials. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2022; 34:304001. [PMID: 35512675 DOI: 10.1088/1361-648x/ac6d3a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/24/2022] [Accepted: 05/05/2022] [Indexed: 06/14/2023]
Abstract
We revisit the concept of nonunitary superconductivity and generalize it to address complex quantum materials. Starting with a brief review of the notion of nonunitary superconductivity, we discuss its spectral signatures in simple models with only the spin as an internal degree of freedom. In complex materials with multiple internal degrees of freedom, there are many more possibilities for the development of nonunitary order parameters. We provide examples focusing on d-electron systems with two orbitals, applicable to a variety of materials. We discuss the consequences for the superconducting spectra, highlighting that gap openings of band crossings at finite energies can be attributed to a nonunitary order parameter if this is associated with a finite superconducting fitness matrix. We speculate that nonunitary superconductivity in complex quantum materials is in fact very common and can be associated with multiple cases of recently reported time-reversal symmetry breaking superconductors.
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Affiliation(s)
- Aline Ramires
- Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
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19
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Wang J, Powers W, Zhang Z, Smith M, McIntosh BJ, Bac SK, Riney L, Zhukovskyi M, Orlova T, Rokhinson LP, Hsu YT, Liu X, Assaf BA. Observation of Coexisting Weak Localization and Superconducting Fluctuations in Strained Sn 1-xIn xTe Thin Films. NANO LETTERS 2022; 22:792-800. [PMID: 35007089 DOI: 10.1021/acs.nanolett.1c04370] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Topological superconductors have attracted tremendous excitement as they are predicted to host Majorana zero modes that can be utilized for topological quantum computing. Candidate topological superconductor Sn1-xInxTe thin films (0 < x < 0.3) grown by molecular beam epitaxy and strained in the (111) plane are shown to host quantum interference effects in the conductivity coexisting with superconducting fluctuations above the critical temperature Tc. An analysis of the normal state magnetoresistance reveals these effects. A crossover from weak antilocalization to localization is consistently observed in superconducting samples, indicating that superconductivity originates dominantly from charge carriers occupying trivial states that may be strongly spin-orbit split. A large enhancement of the conductivity is observed above Tc, indicating the presence of superconducting fluctuations. Our results motivate a re-examination of the debated pairing symmetry of this material when subjected to quantum confinement and lattice strain.
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Affiliation(s)
- Jiashu Wang
- Department of Physics, University of Notre Dame, Notre Dame, Indiana 46556, United States
| | - William Powers
- Department of Physics, University of Notre Dame, Notre Dame, Indiana 46556, United States
| | - Zhan Zhang
- X-ray Science Division, Advanced Photon Source, Argonne National Lab, Lemont, Illinois 60439, United States
| | - Michael Smith
- Department of Physics, University of Notre Dame, Notre Dame, Indiana 46556, United States
| | - Bradlee J McIntosh
- Department of Physics, University of Notre Dame, Notre Dame, Indiana 46556, United States
| | - Seul Ki Bac
- Department of Physics, University of Notre Dame, Notre Dame, Indiana 46556, United States
| | - Logan Riney
- Department of Physics, University of Notre Dame, Notre Dame, Indiana 46556, United States
| | - Maksym Zhukovskyi
- Notre Dame Integrated Imaging Facility, University of Notre Dame, Notre Dame, Indiana 46556, United States
| | - Tatyana Orlova
- Notre Dame Integrated Imaging Facility, University of Notre Dame, Notre Dame, Indiana 46556, United States
| | - Leonid P Rokhinson
- Department of Physics and Astronomy, Purdue University, West Lafayette, Indiana 47907, United States
- Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, United States
- Department of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907, United States
| | - Yi-Ting Hsu
- Department of Physics, University of Notre Dame, Notre Dame, Indiana 46556, United States
| | - Xinyu Liu
- Department of Physics, University of Notre Dame, Notre Dame, Indiana 46556, United States
| | - Badih A Assaf
- Department of Physics, University of Notre Dame, Notre Dame, Indiana 46556, United States
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20
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Jeon KR, Cho K, Chakraborty A, Jeon JC, Yoon J, Han H, Kim JK, Parkin SSP. Role of Two-Dimensional Ising Superconductivity in the Nonequilibrium Quasiparticle Spin-to-Charge Conversion Efficiency. ACS NANO 2021; 15:16819-16827. [PMID: 34597020 PMCID: PMC8552497 DOI: 10.1021/acsnano.1c07192] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/19/2021] [Accepted: 09/29/2021] [Indexed: 06/13/2023]
Abstract
Nonequilibrium studies of two-dimensional (2D) superconductors (SCs) with Ising spin-orbit coupling are prerequisite for their successful application to equilibrium spin-triplet Cooper pairs and, potentially, Majorana Fermions. By taking advantage of the recent discoveries of 2D SCs and their compatibility with any other materials, we fabricate here nonlocal magnon devices to examine how such 2D Ising superconductivity affects the conversion efficiency of magnon spin to quasiparticle charge in superconducting flakes of 2H-NbSe2 transferred onto ferrimagnetic insulating Y3Fe5O12. Comparison with a reference device based on a conventionally paired superconductor shows that the Y3Fe5O12-induced in-plane (IP) exchange spin-splitting in the NbSe2 flake is hindered by its inherent out-of-plane (OOP) spin-orbit field, which, in turn, limits the transition-state enhancement of the spin-to-charge conversion efficiency. Our out-of-equilibrium study highlights the significance of symmetry matching between underlying Cooper pairs and exchange-induced spin-splitting for the giant transition-state spin-to-charge conversion and may have implications toward proximity-engineered spin-polarized triplet pairing via tuning the relative strength of IP exchange and OOP spin-orbit fields in ferromagnetic insulator/2D Ising SC bilayers.
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21
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Qiu D, Gong C, Wang S, Zhang M, Yang C, Wang X, Xiong J. Recent Advances in 2D Superconductors. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2021; 33:e2006124. [PMID: 33768653 DOI: 10.1002/adma.202006124] [Citation(s) in RCA: 33] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/08/2020] [Revised: 10/22/2020] [Indexed: 06/12/2023]
Abstract
The emergence of superconductivity in 2D materials has attracted much attention and there has been rapid development in recent years because of their fruitful physical properties, such as high transition temperature (Tc ), continuous phase transition, and enhanced parallel critical magnetic field (Bc ). Tremendous efforts have been devoted to exploring different physical parameters to figure out the mechanisms behind the unexpected superconductivity phenomena, including adjusting the thickness of samples, fabricating various heterostructures, tuning the carrier density by electric field and chemical doping, and so on. Here, different types of 2D superconductivity with their unique characteristics are introduced, including the conventional Bardeen-Cooper-Schrieffer superconductivity in ultrathin films, high-Tc superconductivity in Fe-based and Cu-based 2D superconductors, unconventional superconductivity in newly discovered twist-angle bilayer graphene, superconductivity with enhanced Bc , and topological superconductivity. A perspective toward this field is then proposed based on academic knowledge from the recently reported literature. The aim is to provide researchers with a clear and comprehensive understanding about the newly developed 2D superconductivity and promote the development of this field much further.
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Affiliation(s)
- Dong Qiu
- State Key Laboratory of Electronic Thin Film and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, 610054, China
| | - Chuanhui Gong
- State Key Laboratory of Electronic Thin Film and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, 610054, China
| | - SiShuang Wang
- State Key Laboratory of Electronic Thin Film and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, 610054, China
| | - Miao Zhang
- State Key Laboratory of Electronic Thin Film and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, 610054, China
| | - Chao Yang
- State Key Laboratory of Electronic Thin Film and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, 610054, China
| | - Xianfu Wang
- State Key Laboratory of Electronic Thin Film and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, 610054, China
| | - Jie Xiong
- State Key Laboratory of Electronic Thin Film and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, 610054, China
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22
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Zhang Q, Huang Z, Hou Y, Yuan P, Xu Z, Yang H, Song X, Chen Y, Yang H, Zhang T, Liu L, Gao HJ, Wang Y. Tuning Molecular Superlattice by Charge-Density-Wave Patterns in Two-Dimensional Monolayer Crystals. J Phys Chem Lett 2021; 12:3545-3551. [PMID: 33818110 DOI: 10.1021/acs.jpclett.1c00230] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Charge density wave (CDW) in two-dimensional (2D) crystals plays a vital role in tuning the interface structures and properties. However, how the CDW tunes the self-assembled molecular superlattice still remains unclear. In this study, we investigated the self-assembled manganese phthalocyanine (MnPc) molecular superlattice on single-layered 1T- and 2H-NbSe2 crystals under regulation by distinct CDW patterns. We observe that, in low coverage, MnPc molecules preferentially adsorb on 2H-NbSe2 compared to 1T-NbSe2. With increasing coverage, MnPc can form a highly ordered superlattice on 2H-NbSe2; however, it is randomly distributed on 1T-NbSe2. We reveal a perfect geometric commensurability between the molecular superlattice and intrinsic CDW pattern in 2H-NbSe2 and a poor commensurability for that of 1T-NbSe2. We believe that the subtly different geometric commensurability dominates the different adsorption and arrangement of the molecular superlattices on 2D CDW patterns. Our study provides a pioneering approach for tuning the molecular superlattices using the CDW patterns.
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Affiliation(s)
- Quanzhen Zhang
- MIIT Key Laboratory for Low-Dimensional Quantum Structure and Devices, School of Information and Electronics, Beijing Institute of Technology, Beijing 100081, China
| | - Zeping Huang
- MIIT Key Laboratory for Low-Dimensional Quantum Structure and Devices, School of Information and Electronics, Beijing Institute of Technology, Beijing 100081, China
| | - Yanhui Hou
- MIIT Key Laboratory for Low-Dimensional Quantum Structure and Devices, School of Information and Electronics, Beijing Institute of Technology, Beijing 100081, China
| | - Peiwen Yuan
- MIIT Key Laboratory for Low-Dimensional Quantum Structure and Devices, School of Information and Electronics, Beijing Institute of Technology, Beijing 100081, China
| | - Ziqiang Xu
- MIIT Key Laboratory for Low-Dimensional Quantum Structure and Devices, School of Information and Electronics, Beijing Institute of Technology, Beijing 100081, China
| | - Han Yang
- MIIT Key Laboratory for Low-Dimensional Quantum Structure and Devices, School of Information and Electronics, Beijing Institute of Technology, Beijing 100081, China
| | - Xuan Song
- MIIT Key Laboratory for Low-Dimensional Quantum Structure and Devices, School of Information and Electronics, Beijing Institute of Technology, Beijing 100081, China
| | - Yaoyao Chen
- MIIT Key Laboratory for Low-Dimensional Quantum Structure and Devices, School of Information and Electronics, Beijing Institute of Technology, Beijing 100081, China
| | - Huixia Yang
- MIIT Key Laboratory for Low-Dimensional Quantum Structure and Devices, School of Information and Electronics, Beijing Institute of Technology, Beijing 100081, China
| | - Teng Zhang
- MIIT Key Laboratory for Low-Dimensional Quantum Structure and Devices, School of Information and Electronics, Beijing Institute of Technology, Beijing 100081, China
| | - Liwei Liu
- MIIT Key Laboratory for Low-Dimensional Quantum Structure and Devices, School of Information and Electronics, Beijing Institute of Technology, Beijing 100081, China
| | - Hong-Jun Gao
- Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Yeliang Wang
- MIIT Key Laboratory for Low-Dimensional Quantum Structure and Devices, School of Information and Electronics, Beijing Institute of Technology, Beijing 100081, China
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23
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Zhao C, Che X, Zhang Z, Huang F. P-type doping in 2M-WS 2 for a complete phase diagram. Dalton Trans 2021; 50:3862-3866. [PMID: 33656509 DOI: 10.1039/d0dt04313c] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
2M-WS2 as a new phase of transition metal dichalcogenides possesses many novel physical properties, such as superconductivity and topological surface states. The effect of n-type doping on the superconductivity of this material has been studied. However, p-type doping has not been studied, because it is difficult to implement p-type doping in metastable 2M-WS2. In this paper, p-type doping was achieved in 2M-WS2 for the first time by using Mo. With the increase of the Mo content, the carrier concentration rises slightly from 1.42 × 1021 cm-1 to 1.56 × 1021 cm-1. Meanwhile, the superconducting transition temperature decreases monotonously with the increase of Mo doping and reaches a minimum value of 4.37 K at the doping limit of x = 0.6 in W1-xMoxS2. Combining the data of n-type doped 2M-WS2 from our previous research, we summarize the carrier concentration and superconducting transition temperature in a phase diagram, which shows a typical dome-like shape. These results uncover the relationship between the carrier concentration and electronic state of 2M-WS2.
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Affiliation(s)
- Chendong Zhao
- State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, P.R. China.
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24
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Kumar S, Suryanarayana P. Bending moduli for forty-four select atomic monolayers from first principles. NANOTECHNOLOGY 2020; 31:43LT01. [PMID: 32619990 DOI: 10.1088/1361-6528/aba2a2] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
We calculate bending moduli along the principal directions for forty-four select atomic monolayers using ab initio density functional theory (DFT). Specifically, considering representative materials from each of Groups IV, III-V, V monolayers, Group IV monochalcogenides, transition metal trichalcogenides, transition metal dichalcogenides and Group III monochalcogenides, we utilize the recently developed Cyclic DFT method to calculate the bending moduli in the practically relevant but previously intractable low-curvature limit. We find that the moduli generally increase with thickness of the monolayer, while spanning three orders of magnitude between the different materials. In addition, structures with a rectangular lattice are prone to a higher degree of anisotropy relative to those with a honeycomb lattice. Exceptions to these trends are generally a consequence of unusually strong/weak bonding and/or significant structural relxation related effects.
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Affiliation(s)
- Shashikant Kumar
- College of Engineering, Georgia Institute of Technology, Atlanta, GA 30332, United States of America
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25
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Hsu YT, Cole WS, Zhang RX, Sau JD. Inversion-Protected Higher-Order Topological Superconductivity in Monolayer WTe_{2}. PHYSICAL REVIEW LETTERS 2020; 125:097001. [PMID: 32915630 DOI: 10.1103/physrevlett.125.097001] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/21/2019] [Accepted: 08/06/2020] [Indexed: 06/11/2023]
Abstract
Monolayer WTe_{2}, a centrosymmetric transition metal dichacogenide, has recently been established as a quantum spin Hall insulator and found superconducting upon gating. Here we study the pairing symmetry and topological nature of superconducting WTe_{2} with a microscopic model at mean-field level. Surprisingly, we find that the spin-triplet phases in our phase diagram all host Majorana modes localized on two opposite corners. Even when the conventional pairing is favored, we find that an intermediate in-plane magnetic field exceeding the Pauli limit stabilizes an unconventional equal-spin pairing aligning with the field, which also hosts Majorana corner modes. Motivated by our findings, we obtain a recipe for two-dimensional superconductors featuring "higher-order topology" from the boundary perspective. Generally, a superconducting inversion-symmetric quantum spin Hall material whose normal-state Fermi surface is away from high-symmetry points, such as gated monolayer WTe_{2}, hosts Majorana corner modes if the superconductivity is parity-odd. We further point out that this higher-order phase is an inversion-protected topological crystalline superconductor and study the bulk-boundary correspondence. Finally, we discuss possible experiments for probing the Majorana corner modes. Our findings suggest superconducting monolayer WTe_{2} is a playground for higher-order topological superconductivity and possibly the first material realization for inversion-protected Majorana corner modes without utilizing proximity effect.
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Affiliation(s)
- Yi-Ting Hsu
- Condensed Matter Theory Center and Joint Quantum Institute, University of Maryland, College Park, Maryland 20742, USA
| | - William S Cole
- Condensed Matter Theory Center and Joint Quantum Institute, University of Maryland, College Park, Maryland 20742, USA
| | - Rui-Xing Zhang
- Condensed Matter Theory Center and Joint Quantum Institute, University of Maryland, College Park, Maryland 20742, USA
| | - Jay D Sau
- Condensed Matter Theory Center and Joint Quantum Institute, University of Maryland, College Park, Maryland 20742, USA
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26
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Chen C, Das P, Aytan E, Zhou W, Horowitz J, Satpati B, Balandin AA, Lake RK, Wei P. Strain-Controlled Superconductivity in Few-Layer NbSe 2. ACS APPLIED MATERIALS & INTERFACES 2020; 12:38744-38750. [PMID: 32805977 DOI: 10.1021/acsami.0c08804] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
The controlled tunability of superconductivity in low-dimensional materials may enable new quantum devices. Particularly in triplet or topological superconductors, tunneling devices such as Josephson junctions, etc., can demonstrate exotic functionalities. The tunnel barrier, an insulating or normal material layer separating two superconductors, is a key component for the junctions. Thin layers of NbSe2 have been shown as a superconductor with strong spin orbit coupling, which can give rise to topological superconductivity if driven by a large magnetic exchange field. Here we demonstrate the superconductor-insulator transitions in epitaxially grown few-layer NbSe2 with wafer-scale uniformity on insulating substrates. We provide the electrical transport, Raman spectroscopy, cross-sectional transmission electron microscopy, and X-ray diffraction characterizations of the insulating phase. We show that the superconductor-insulator transition is driven by strain, which also causes characteristic energy shifts of the Raman modes. Our observation paves the way for high-quality heterojunction tunnel barriers to be seamlessly built into epitaxial NbSe2 itself, thereby enabling highly scalable tunneling devices for superconductor-based quantum electronics.
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Affiliation(s)
- Cliff Chen
- Department of Physics and Astronomy, University of California, Riverside, California 92521, United States
| | - Protik Das
- Department of Electrical and Computer Engineering, University of California, Riverside, California 92521, United States
| | - Ece Aytan
- Department of Electrical and Computer Engineering, University of California, Riverside, California 92521, United States
| | - Weimin Zhou
- Department of Physics and Astronomy, University of California, Riverside, California 92521, United States
| | - Justin Horowitz
- Department of Physics and Astronomy, University of California, Riverside, California 92521, United States
| | - Biswarup Satpati
- Surface Physics & Material Science Division, Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700 064, India
| | - Alexander A Balandin
- Department of Electrical and Computer Engineering, University of California, Riverside, California 92521, United States
| | - Roger K Lake
- Department of Electrical and Computer Engineering, University of California, Riverside, California 92521, United States
| | - Peng Wei
- Department of Physics and Astronomy, University of California, Riverside, California 92521, United States
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27
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Zeytinoğlu S, İmamoğlu A, Huber S. Tunable Flux Vortices in Two-Dimensional Dirac Superconductors. PHYSICAL REVIEW LETTERS 2020; 124:207006. [PMID: 32501063 DOI: 10.1103/physrevlett.124.207006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/17/2019] [Revised: 10/15/2019] [Accepted: 02/24/2020] [Indexed: 06/11/2023]
Abstract
The nontrivial geometry encoded in the quantum mechanical wave function has important consequences for both noninteracting and interacting systems. Yet, our understanding of the relationship between geometrical effects in noninteracting systems and their interacting counterparts is far from complete. Here, we demonstrate how the single-particle Berry curvature associated with the normal phase in two dimensions modifies the fluxoid quantization of a Bardeen-Cooper-Schrieffer superconductor. A discussion of the experimental scenarios where this anomalous quantization is expected is provided. Our work demonstrates the importance of variational Ansätze in making a clear connection between the Berry phases of single-particle and many-body wave functions.
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Affiliation(s)
- Sina Zeytinoğlu
- Institute for Theoretical Physics, ETH Zürich, CH-8093 Zurich, Switzerland
- Institute for Quantum Electronics, ETH Zürich, CH-8093 Zurich, Switzerland
- Department of Physics, Harvard University, Cambridge, Massachusetts, 02138, USA
| | - Atac İmamoğlu
- Institute for Quantum Electronics, ETH Zürich, CH-8093 Zurich, Switzerland
| | - Sebastian Huber
- Institute for Theoretical Physics, ETH Zürich, CH-8093 Zurich, Switzerland
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28
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Trainer DJ, Wang B, Bobba F, Samuelson N, Xi X, Zasadzinski J, Nieminen J, Bansil A, Iavarone M. Proximity-Induced Superconductivity in Monolayer MoS 2. ACS NANO 2020; 14:2718-2728. [PMID: 31930912 DOI: 10.1021/acsnano.9b07475] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
Proximity effects in superconducting normal (SN) material heterostructures with metals and semiconductors have long been observed and theoretically described in terms of Cooper pair wave functions and Andreev reflections. Whereas the semiconducting N-layer materials in the proximity experiments to date have been doped and tens of nanometers thick, we present here a proximity tunneling study involving a pristine single-layer transition-metal dichalcogenide film of MoS2 placed on top of a Pb thin film. Scanning tunneling microscopy and spectroscopy experiments together with parallel theoretical analysis based on electronic structure calculations and Green's function modeling allow us to unveil a two-step process in which MoS2 first becomes metallic and then is induced into becoming a conventional s-wave Bardeen-Cooper-Schrieffer-type superconductor. The lattice mismatch between the MoS2 overlayer and the Pb substrate is found to give rise to a topographic moiré pattern. Even though the induced gap appears uniform in location, the coherence peak height of the tunneling spectra is modulated spatially into a moiré pattern that is similar to but shifted with respect to the moiré pattern observed in topography. The aforementioned modulation is shown to originate from the atomic-scale structure of the SN interface and the nature of local atomic orbitals that are involved in generating the local pairing potential. Our study indicates that the local modulation of induced superconductivity in MoS2 could be controlled via geometrical tuning, and it thus shows promise toward the integration of monolayer superconductors into next-generation functional electronic devices by exploiting proximity-effect control of quantum phases.
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Affiliation(s)
- Daniel J Trainer
- Physics Department, Temple University, Philadelphia, Pennsylvania 19122, United States
| | - BaoKai Wang
- Physics Department, Northeastern University, Boston, Massachusetts 02115, United States
| | - Fabrizio Bobba
- Physics Department, Temple University, Philadelphia, Pennsylvania 19122, United States
- Physics Department, University of Salerno, Fisciano 84084, Italy
| | - Noah Samuelson
- Physics Department, Illinois Institute of Technology, Chicago, Illinois 60616, United States
| | - Xiaoxing Xi
- Physics Department, Temple University, Philadelphia, Pennsylvania 19122, United States
| | - John Zasadzinski
- Physics Department, Illinois Institute of Technology, Chicago, Illinois 60616, United States
| | - Jouko Nieminen
- Physics Department, Northeastern University, Boston, Massachusetts 02115, United States
- Computational Physics Laboratory, Tampere University, Tampere 33014, Finland
| | - Arun Bansil
- Physics Department, Northeastern University, Boston, Massachusetts 02115, United States
| | - Maria Iavarone
- Physics Department, Temple University, Philadelphia, Pennsylvania 19122, United States
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29
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Huang HH, Fan X, Singh DJ, Zheng WT. Recent progress of TMD nanomaterials: phase transitions and applications. NANOSCALE 2020; 12:1247-1268. [PMID: 31912836 DOI: 10.1039/c9nr08313h] [Citation(s) in RCA: 53] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Transition metal dichalcogenides (TMDs) show wide ranges of electronic properties ranging from semiconducting, semi-metallic to metallic due to their remarkable structural differences. To obtain 2D TMDs with specific properties, it is extremely important to develop particular strategies to obtain specific phase structures. Phase engineering is a traditional method to achieve transformation from one phase to another controllably. Control of such transformations enables the control of properties and access to a range of properties, otherwise inaccessible. Then extraordinary structural, electronic and optical properties lead to a broad range of potential applications. In this review, we introduce the various electronic properties of 2D TMDs and their polymorphs, and strategies and mechanisms for phase transitions, and phase transition kinetics. Moreover, the potential applications of 2D TMDs in energy storage and conversion, including electro/photocatalysts, batteries/supercapacitors and electronic devices, are also discussed. Finally, opportunities and challenges are highlighted. This review may further promote the development of TMD phase engineering and shed light on other two-dimensional materials of fundamental interest and with potential ranges of applications.
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Affiliation(s)
- H H Huang
- Key Laboratory of Automobile Materials (Jilin University), Ministry of Education, and College of Materials Science and Engineering, Jilin University, Changchun, 130012, China.
| | - Xiaofeng Fan
- Key Laboratory of Automobile Materials (Jilin University), Ministry of Education, and College of Materials Science and Engineering, Jilin University, Changchun, 130012, China.
| | - David J Singh
- Department of Physics and Astronomy, University of Missouri, Columbia, Missouri 65211-7010, USA and Department of Chemistry, University of Missouri, Columbia, Missouri 65211, USA
| | - W T Zheng
- Key Laboratory of Automobile Materials (Jilin University), Ministry of Education, and College of Materials Science and Engineering, Jilin University, Changchun, 130012, China. and State Key Laboratory of Automotive Simulation and Control, Jilin University, Changchun 130012, China.
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30
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Li X, Zhang Z, Zhang H. High throughput study on magnetic ground states with Hubbard U corrections in transition metal dihalide monolayers. NANOSCALE ADVANCES 2020; 2:495-501. [PMID: 36134001 PMCID: PMC9419158 DOI: 10.1039/c9na00588a] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/18/2019] [Accepted: 12/03/2019] [Indexed: 06/12/2023]
Abstract
We present a high throughput study of the magnetic ground states for 90 transition metal dihalide monolayers TMX2 using density functional theory based on a collection of Hubbard U values. Stable geometrical phases between 2H and 1T are first determined. Spin-polarized calculations show that 50 out of 55 magnetic TMX2 monolayers are energetically prone to the 1T phase. Further, the magnetic ground states are determined by considering four local spin models with respect to different U values. Interestingly, 23 out of 55 TMX2 monolayers exhibit robust magnetic ground orderings which will not be changed by the U values. Among them, NiCl2 with a magnetic moment of 2 μ B is a ferromagnetic (FM) insulator, while the VX2, MnX2 (X = Cl, Br and I), PtCl2 and CoI2 monolayers have noncollinear antiferromagnetic (120°-AFM) ground states with a tiny in-plane magnetic anisotropic energy, indicating flexible magnetic orientation rotation. The exchange parameters for both robust FM and 120°-AFM systems are analyzed in detail with the Heisenberg model. Our high-throughput calculations give a systematic study of the electronic and magnetic properties of TMX2 monolayers, and these two-dimensional materials with versatile magnetic behavior may have great potential for spintronic applications.
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Affiliation(s)
- Xinru Li
- College of Physics and Optoelectronic Engineering, Shenzhen University 518060 Shenzhen P. R. China
- Institute of Materials Science, Darmstadt University of Technology 64287 Darmstadt Germany
| | - Zeying Zhang
- College of Mathematics and Physics, Beijing University of Chemical Technology 100029 Beijing P. R. China
- Institute of Materials Science, Darmstadt University of Technology 64287 Darmstadt Germany
| | - Hongbin Zhang
- Institute of Materials Science, Darmstadt University of Technology 64287 Darmstadt Germany
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31
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Kayyalha M, Xiao D, Zhang R, Shin J, Jiang J, Wang F, Zhao YF, Xiao R, Zhang L, Fijalkowski KM, Mandal P, Winnerlein M, Gould C, Li Q, Molenkamp LW, Chan MHW, Samarth N, Chang CZ. Absence of evidence for chiral Majorana modes in quantum anomalous Hall-superconductor devices. Science 2020; 367:64-67. [DOI: 10.1126/science.aax6361] [Citation(s) in RCA: 70] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2019] [Accepted: 11/07/2019] [Indexed: 11/02/2022]
Affiliation(s)
- Morteza Kayyalha
- Department of Physics, Pennsylvania State University, University Park, PA 16802, USA
| | - Di Xiao
- Department of Physics, Pennsylvania State University, University Park, PA 16802, USA
| | - Ruoxi Zhang
- Department of Physics, Pennsylvania State University, University Park, PA 16802, USA
| | - Jaeho Shin
- Department of Physics, Pennsylvania State University, University Park, PA 16802, USA
| | - Jue Jiang
- Department of Physics, Pennsylvania State University, University Park, PA 16802, USA
| | - Fei Wang
- Department of Physics, Pennsylvania State University, University Park, PA 16802, USA
| | - Yi-Fan Zhao
- Department of Physics, Pennsylvania State University, University Park, PA 16802, USA
| | - Run Xiao
- Department of Physics, Pennsylvania State University, University Park, PA 16802, USA
| | - Ling Zhang
- Department of Physics, Pennsylvania State University, University Park, PA 16802, USA
| | - Kajetan M. Fijalkowski
- Faculty for Physics and Astronomy (EP3), University of Würzburg, Am Hubland, D-97074 Würzburg, Germany
- Institute for Topological Insulators, Am Hubland, D-97074 Würzburg, Germany
| | - Pankaj Mandal
- Faculty for Physics and Astronomy (EP3), University of Würzburg, Am Hubland, D-97074 Würzburg, Germany
- Institute for Topological Insulators, Am Hubland, D-97074 Würzburg, Germany
| | - Martin Winnerlein
- Faculty for Physics and Astronomy (EP3), University of Würzburg, Am Hubland, D-97074 Würzburg, Germany
- Institute for Topological Insulators, Am Hubland, D-97074 Würzburg, Germany
| | - Charles Gould
- Faculty for Physics and Astronomy (EP3), University of Würzburg, Am Hubland, D-97074 Würzburg, Germany
- Institute for Topological Insulators, Am Hubland, D-97074 Würzburg, Germany
| | - Qi Li
- Department of Physics, Pennsylvania State University, University Park, PA 16802, USA
| | - Laurens W. Molenkamp
- Faculty for Physics and Astronomy (EP3), University of Würzburg, Am Hubland, D-97074 Würzburg, Germany
- Institute for Topological Insulators, Am Hubland, D-97074 Würzburg, Germany
| | - Moses H. W. Chan
- Department of Physics, Pennsylvania State University, University Park, PA 16802, USA
| | - Nitin Samarth
- Department of Physics, Pennsylvania State University, University Park, PA 16802, USA
| | - Cui-Zu Chang
- Department of Physics, Pennsylvania State University, University Park, PA 16802, USA
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32
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Rigosi AF, Hill HM, Krylyuk S, Nguyen NV, Hight Walker AR, Davydov AV, Newell DB. Dielectric Properties of Nb xW 1-xSe 2 Alloys. JOURNAL OF RESEARCH OF THE NATIONAL INSTITUTE OF STANDARDS AND TECHNOLOGY 2019; 124:1-10. [PMID: 34877178 PMCID: PMC7343519 DOI: 10.6028/jres.124.035] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 11/25/2019] [Indexed: 06/13/2023]
Abstract
The growth of transition metal dichalcogenide (TMDC) alloys provides an opportunity to experimentally access information elucidating how optical properties change with gradual substitutions in the lattice compared with their pure compositions. In this work, we performed growths of alloyed crystals with stoichiometric compositions between pure forms of NbSe2 and WSe2, followed by an optical analysis of those alloys by utilizing Raman spectroscopy and spectroscopic ellipsometry.
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Affiliation(s)
- Albert F Rigosi
- National Institute of Standards and Technology, Gaithersburg, MD 20899, USA
| | - Heather M Hill
- National Institute of Standards and Technology, Gaithersburg, MD 20899, USA
| | | | - Nhan V Nguyen
- National Institute of Standards and Technology, Gaithersburg, MD 20899, USA
| | | | - Albert V Davydov
- National Institute of Standards and Technology, Gaithersburg, MD 20899, USA
| | - David B Newell
- National Institute of Standards and Technology, Gaithersburg, MD 20899, USA
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33
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Aggarwal L, Singh CK, Aslam M, Singha R, Pariari A, Gayen S, Kabir M, Mandal P, Sheet G. Tip-induced superconductivity coexisting with preserved topological properties in line-nodal semimetal ZrSiS. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2019; 31:485707. [PMID: 31486414 DOI: 10.1088/1361-648x/ab3b61] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
ZrSiS was recently shown to be a new material with topologically non-trivial band structure that exhibits multiple Dirac nodes and a robust linear band dispersion up to an unusually high energy of 2 eV. Such a robust linear dispersion makes the topological properties of ZrSiS insensitive to perturbations like carrier doping or lattice distortion. Here, we show that a novel superconducting phase with a remarkably high [Formula: see text] of 7.5 K can be induced in single crystals of ZrSiS by a non-superconducting metallic tip of Ag. From first-principles calculations, we show that the observed superconducting phase might originate from a dramatic enhancement of density of states due to the presence of a metallic tip on ZrSiS. Our calculations also show that the emerging tip-induced superconducting phase co-exists with the well preserved topological properties of ZrSiS.
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Affiliation(s)
- Leena Aggarwal
- Department of Physical Sciences, Indian Institute of Science Education and Research Mohali, Sector 81, S. A. S. Nagar, PO: 140306, Manauli, India
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34
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Cui J, Li P, Zhou J, He WY, Huang X, Yi J, Fan J, Ji Z, Jing X, Qu F, Cheng ZG, Yang C, Lu L, Suenaga K, Liu J, Law KT, Lin J, Liu Z, Liu G. Transport evidence of asymmetric spin-orbit coupling in few-layer superconducting 1T d-MoTe 2. Nat Commun 2019; 10:2044. [PMID: 31053717 PMCID: PMC6499809 DOI: 10.1038/s41467-019-09995-0] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2018] [Accepted: 04/09/2019] [Indexed: 11/09/2022] Open
Abstract
Two-dimensional transition metal dichalcogenides MX2 (M = W, Mo, Nb, and X = Te, Se, S) with strong spin-orbit coupling possess plenty of novel physics including superconductivity. Due to the Ising spin-orbit coupling, monolayer NbSe2 and gated MoS2 of 2H structure can realize the Ising superconductivity, which manifests itself with in-plane upper critical field far exceeding Pauli paramagnetic limit. Surprisingly, we find that a few-layer 1Td structure MoTe2 also exhibits an in-plane upper critical field which goes beyond the Pauli paramagnetic limit. Importantly, the in-plane upper critical field shows an emergent two-fold symmetry which is different from the isotropic in-plane upper critical field in 2H transition metal dichalcogenides. We show that this is a result of an asymmetric spin-orbit coupling in 1Td transition metal dichalcogenides. Our work provides transport evidence of a new type of asymmetric spin-orbit coupling in transition metal dichalcogenides which may give rise to novel superconducting and spin transport properties.
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Affiliation(s)
- Jian Cui
- Beijing National Laboratory of Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, 100190, Beijing, China
| | - Peiling Li
- Beijing National Laboratory of Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, 100190, Beijing, China.,University of Chinese Academy of Sciences, 100049, Beijing, China
| | - Jiadong Zhou
- School of Materials Science and Engineering, Nanyang Technological University, Singapore, 639798, Singapore
| | - Wen-Yu He
- Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China
| | - Xiangwei Huang
- Beijing National Laboratory of Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, 100190, Beijing, China.,University of Chinese Academy of Sciences, 100049, Beijing, China
| | - Jian Yi
- Ningbo Institute of Industrial Technology, Chinese Academy of Sciences, 315201, Ningbo, China
| | - Jie Fan
- Beijing National Laboratory of Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, 100190, Beijing, China
| | - Zhongqing Ji
- Beijing National Laboratory of Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, 100190, Beijing, China
| | - Xiunian Jing
- Beijing National Laboratory of Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, 100190, Beijing, China.,Collaborative Innovation Center of Quantum Matter, 100871, Beijing, China
| | - Fanming Qu
- Beijing National Laboratory of Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, 100190, Beijing, China
| | - Zhi Gang Cheng
- Beijing National Laboratory of Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, 100190, Beijing, China
| | - Changli Yang
- Beijing National Laboratory of Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, 100190, Beijing, China.,Collaborative Innovation Center of Quantum Matter, 100871, Beijing, China
| | - Li Lu
- Beijing National Laboratory of Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, 100190, Beijing, China.,Collaborative Innovation Center of Quantum Matter, 100871, Beijing, China
| | - Kazu Suenaga
- National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, 305-8565, Japan
| | - Junwei Liu
- Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China
| | - Kam Tuen Law
- Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China
| | - Junhao Lin
- Department of Physics, Southern University of Science and Technology, 518055, Shenzhen, China. .,Shenzhen Key Laboratory of Quantum Science and Engineering, 518055, Shenzhen, China.
| | - Zheng Liu
- School of Materials Science and Engineering, Nanyang Technological University, Singapore, 639798, Singapore.
| | - Guangtong Liu
- Beijing National Laboratory of Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, 100190, Beijing, China. .,Songshan Lake Materials Laboratory, Dongguan, 523808, Guangdong, China.
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35
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Piatti E, Romanin D, Gonnelli RS. Mapping multi-valley Lifshitz transitions induced by field-effect doping in strained MoS 2 nanolayers. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2019; 31:114002. [PMID: 30562728 DOI: 10.1088/1361-648x/aaf981] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Gate-induced superconductivity at the surface of nanolayers of semiconducting transition metal dichalcogenides (TMDs) has attracted a lot of attention in recent years, thanks to the sizeable transition temperature, robustness against in-plane magnetic fields beyond the Pauli limit, and hints to a non-conventional nature of the pairing. A key information necessary to unveil its microscopic origin is the geometry of the Fermi surface hosting the Cooper pairs as a function of field-effect doping, which is dictated by the filling of the inequivalent valleys at the K/K[Formula: see text] and Q/Q[Formula: see text] points of the Brillouin zone. Here, we achieve this by combining density functional theory calculations of the bandstructure with transport measurements on ion-gated 2H-MoS2 nanolayers. We show that, when the number of layers and the amount of strain are set to their experimental values, the Fermi level crosses the bottom of the high-energy valleys at Q/Q[Formula: see text] at doping levels where characteristic kinks in the transconductance are experimentally detected. We also develop a simple 2D model which is able to quantitatively describe the broadening of the kinks observed upon increasing temperature. We demonstrate that this combined approach can be employed to map the dependence of the Fermi surface of TMD nanolayers on field-effect doping, detect Lifshitz transitions, and provide a method to determine the amount of strain and spin-orbit splitting between sub-bands from electric transport measurements in real devices.
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Affiliation(s)
- Erik Piatti
- Department of Applied Science and Technology, Politecnico di Torino, 10129 Torino, Italy
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36
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Venderley J, Kim EA. Evidence of pair-density wave in spin-valley locked systems. SCIENCE ADVANCES 2019; 5:eaat4698. [PMID: 30944848 PMCID: PMC6440755 DOI: 10.1126/sciadv.aat4698] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/04/2018] [Accepted: 02/08/2019] [Indexed: 06/09/2023]
Abstract
Cooper pairs with a finite center-of-mass momentum form a remarkable state in which the superconducting order parameter is modulated periodically in space. Although intense interest in such a "pair-density wave" (PDW) state has emerged due to recent discoveries in high T c superconductors, there is little theoretical understanding of the mechanism driving this exotic state. The challenge is that many competing states lie close in energy in seemingly simple models, such as the Hubbard model, in the strongly correlated regime. Here, we show that inversion symmetry breaking and the resulting spin-valley locking can promote PDWs over more commonly found spin stripes through frustration against magnetic order. Specifically, we find the first robust evidence for a PDW within density matrix renormalization group simulation of a simple fermionic model. Our results point to a tantalizing possibility in hole-doped group VI transition metal dichalcogenides, with spin-valley locked band structure and moderate correlations.
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37
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Eren I, Iyikanat F, Sahin H. Defect tolerant and dimension dependent ferromagnetism in MnSe2. Phys Chem Chem Phys 2019; 21:16718-16725. [DOI: 10.1039/c9cp03112j] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
By performing density functional theory-based calculations, we investigate the structural, vibrational, electronic and magnetic properties of 2D monolayers, nanoribbons and quantum dots of MnSe2.
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Affiliation(s)
- I. Eren
- Department of Physics
- Izmir Institute of Technology
- Izmir
- Turkey
| | - F. Iyikanat
- Department of Physics
- Izmir Institute of Technology
- Izmir
- Turkey
| | - H. Sahin
- Department of Photonics
- Izmir Institute of Technology
- Izmir
- Turkey
- ICTP-ECAR Eurasian Center for Advanced Research
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38
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Piatti E, De Fazio D, Daghero D, Tamalampudi SR, Yoon D, Ferrari AC, Gonnelli RS. Multi-Valley Superconductivity in Ion-Gated MoS 2 Layers. NANO LETTERS 2018; 18:4821-4830. [PMID: 29949374 DOI: 10.1021/acs.nanolett.8b01390] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Layers of transition metal dichalcogenides (TMDs) combine the enhanced effects of correlations associated with the two-dimensional limit with electrostatic control over their phase transitions by means of an electric field. Several semiconducting TMDs, such as MoS2, develop superconductivity (SC) at their surface when doped with an electrostatic field, but the mechanism is still debated. It is often assumed that Cooper pairs reside only in the two electron pockets at the K/K' points of the Brillouin Zone. However, experimental and theoretical results suggest that a multivalley Fermi surface (FS) is associated with the SC state, involving six electron pockets at Q/Q'. Here, we perform low-temperature transport measurements in ion-gated MoS2 flakes. We show that a fully multivalley FS is associated with the SC onset. The Q/Q' valleys fill for doping ≳ 2 × 1013 cm-2, and the SC transition does not appear until the Fermi level crosses both spin-orbit split sub-bands Q 1 and Q 2. The SC state is associated with the FS connectivity and promoted by a Lifshitz transition due to the simultaneous population of multiple electron pockets. This FS topology will serve as a guideline in the quest for new superconductors.
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Affiliation(s)
- Erik Piatti
- Department of Applied Science and Technology , Politecnico di Torino , 10129 Torino , Italy
| | - Domenico De Fazio
- Cambridge Graphene Centre , University of Cambridge , Cambridge CB3 OFA , United Kingdom
| | - Dario Daghero
- Department of Applied Science and Technology , Politecnico di Torino , 10129 Torino , Italy
| | | | - Duhee Yoon
- Cambridge Graphene Centre , University of Cambridge , Cambridge CB3 OFA , United Kingdom
| | - Andrea C Ferrari
- Cambridge Graphene Centre , University of Cambridge , Cambridge CB3 OFA , United Kingdom
| | - Renato S Gonnelli
- Department of Applied Science and Technology , Politecnico di Torino , 10129 Torino , Italy
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39
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Sohn E, Xi X, He WY, Jiang S, Wang Z, Kang K, Park JH, Berger H, Forró L, Law KT, Shan J, Mak KF. An unusual continuous paramagnetic-limited superconducting phase transition in 2D NbSe 2. NATURE MATERIALS 2018; 17:504-508. [PMID: 29713039 DOI: 10.1038/s41563-018-0061-1] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/09/2017] [Accepted: 03/16/2018] [Indexed: 06/08/2023]
Abstract
Time reversal and spatial inversion are two key symmetries for conventional Bardeen-Cooper-Schrieffer (BCS) superconductivity 1 . Breaking inversion symmetry can lead to mixed-parity Cooper pairing and unconventional superconducting properties1-5. Two-dimensional (2D) NbSe2 has emerged as a new non-centrosymmetric superconductor with the unique out-of-plane or Ising spin-orbit coupling (SOC)6-9. Here we report the observation of an unusual continuous paramagnetic-limited superconductor-normal metal transition in 2D NbSe2. Using tunelling spectroscopy under high in-plane magnetic fields, we observe a continuous closing of the superconducting gap at the upper critical field at low temperatures, in stark contrast to the abrupt first-order transition observed in BCS thin-film superconductors10-12. The paramagnetic-limited continuous transition arises from a large spin susceptibility of the superconducting phase due to the Ising SOC. The result is further supported by self-consistent mean-field calculations based on the ab initio band structure of 2D NbSe2. Our findings establish 2D NbSe2 as a promising platform to explore novel spin-dependent superconducting phenomena and device concepts 1 , such as equal-spin Andreev reflection 13 and topological superconductivity14-16.
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Affiliation(s)
- Egon Sohn
- Department of Physics, The Pennsylvania State University, University Park, PA, USA
- Department of Physics and School of Applied and Engineering Physics, Cornell University, Ithaca, NY, USA
| | - Xiaoxiang Xi
- Department of Physics, The Pennsylvania State University, University Park, PA, USA
- National Laboratory of Solid State Microstructures, School of Physics, and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, China
| | - Wen-Yu He
- Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China
| | - Shengwei Jiang
- Department of Physics, The Pennsylvania State University, University Park, PA, USA
- Department of Physics and School of Applied and Engineering Physics, Cornell University, Ithaca, NY, USA
| | - Zefang Wang
- Department of Physics, The Pennsylvania State University, University Park, PA, USA
- Department of Physics and School of Applied and Engineering Physics, Cornell University, Ithaca, NY, USA
| | - Kaifei Kang
- Department of Physics, The Pennsylvania State University, University Park, PA, USA
- Department of Physics and School of Applied and Engineering Physics, Cornell University, Ithaca, NY, USA
| | - Ju-Hyun Park
- National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL, USA
| | - Helmuth Berger
- Institute of Condensed Matter Physics, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
| | - László Forró
- Institute of Condensed Matter Physics, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
| | - Kam Tuen Law
- Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China
| | - Jie Shan
- Department of Physics, The Pennsylvania State University, University Park, PA, USA.
- Department of Physics and School of Applied and Engineering Physics, Cornell University, Ithaca, NY, USA.
- Kavli Institute at Cornell for Nanoscale Science, Ithaca, NY, USA.
| | - Kin Fai Mak
- Department of Physics, The Pennsylvania State University, University Park, PA, USA.
- Department of Physics and School of Applied and Engineering Physics, Cornell University, Ithaca, NY, USA.
- Kavli Institute at Cornell for Nanoscale Science, Ithaca, NY, USA.
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40
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Costanzo D, Zhang H, Reddy BA, Berger H, Morpurgo AF. Tunnelling spectroscopy of gate-induced superconductivity in MoS 2. NATURE NANOTECHNOLOGY 2018; 13:483-488. [PMID: 29713077 DOI: 10.1038/s41565-018-0122-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2017] [Accepted: 03/23/2018] [Indexed: 06/08/2023]
Abstract
The ability to gate-induce superconductivity by electrostatic charge accumulation is a recent breakthrough in physics and nanoelectronics. With the exception of LaAlO3/SrTiO3 interfaces, experiments on gate-induced superconductors have been largely confined to resistance measurements, which provide very limited information about the superconducting state. Here, we explore gate-induced superconductivity in MoS2 by performing tunnelling spectroscopy to determine the energy-dependent density of states (DOS) for different levels of electron density n. In the superconducting state, the DOS is strongly suppressed at energy smaller than the gap Δ, which is maximum (Δ ~2 meV) for n of ~1 × 1014 cm-2 and decreases monotonously for larger n. A perpendicular magnetic field B generates states at E < Δ that fill the gap, but a 20% DOS suppression of superconducting origin unexpectedly persists much above the transport critical field. Conversely, an in-plane field up to 10 T leaves the DOS entirely unchanged. Our measurements exclude that the superconducting state in MoS2 is fully gapped and reveal the presence of a DOS that vanishes linearly with energy, the explanation of which requires going beyond a conventional, purely phonon-driven Bardeen-Cooper-Schrieffer mechanism.
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Affiliation(s)
| | - Haijing Zhang
- DQMP and GAP, Université de Genève, Geneva, Switzerland
| | | | - Helmuth Berger
- Institut de Physique de la Matière Complexe, Ecole Polytechnique Federale de Lausanne, Lausanne, Switzerland
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41
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Pressure induced superconductivity bordering a charge-density-wave state in NbTe 4 with strong spin-orbit coupling. Sci Rep 2018; 8:6298. [PMID: 29674609 PMCID: PMC5908920 DOI: 10.1038/s41598-018-24572-z] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2017] [Accepted: 04/06/2018] [Indexed: 11/12/2022] Open
Abstract
Transition-metal chalcogenides host various phases of matter, such as charge-density wave (CDW), superconductors, and topological insulators or semimetals. Superconductivity and its competition with CDW in low-dimensional compounds have attracted much interest and stimulated considerable research. Here we report pressure induced superconductivity in a strong spin-orbit (SO) coupled quasi-one-dimensional (1D) transition-metal chalcogenide NbTe4, which is a CDW material under ambient pressure. With increasing pressure, the CDW transition temperature is gradually suppressed, and superconducting transition, which is fingerprinted by a steep resistivity drop, emerges at pressures above 12.4 GPa. Under pressure p = 69 GPa, zero resistance is detected with a transition temperature Tc = 2.2 K and an upper critical field μ0Hc2 = 2 T. We also find large magnetoresistance (MR) up to 102% at low temperatures, which is a distinct feature differentiating NbTe4 from other conventional CDW materials.
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42
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Lee KH, Lee C, Min H, Chung SB. Phase Transitions of the Polariton Condensate in 2D Dirac Materials. PHYSICAL REVIEW LETTERS 2018; 120:157601. [PMID: 29756851 DOI: 10.1103/physrevlett.120.157601] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/01/2017] [Indexed: 06/08/2023]
Abstract
For the quantum well in an optical microcavity, the interplay of the Coulomb interaction and the electron-photon (e-ph) coupling can lead to the hybridizations of the exciton and the cavity photon known as polaritons, which can form the Bose-Einstein condensate above a threshold density. Additional physics due to the nontrivial Berry phase comes into play when the quantum well consists of the gapped two-dimensional Dirac material such as the transition metal dichalcogenide MoS_{2} or WSe_{2}. Specifically, in forming the polariton, the e-ph coupling from the optical selection rule due to the Berry phase can compete against the Coulomb electron-electron (e-e) interaction. We find that this competition gives rise to a rich phase diagram for the polariton condensate involving both topological and symmetry breaking phase transitions, with the former giving rise to the quantum anomalous Hall and the quantum spin Hall phases.
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Affiliation(s)
- Ki Hoon Lee
- Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul National University, Seoul 08826, Korea
- Department of Physics and Astronomy, Seoul National University, Seoul 08826, Korea
| | - Changhee Lee
- Department of Physics and Astronomy, Seoul National University, Seoul 08826, Korea
| | - Hongki Min
- Department of Physics and Astronomy, Seoul National University, Seoul 08826, Korea
| | - Suk Bum Chung
- Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul National University, Seoul 08826, Korea
- Department of Physics and Astronomy, Seoul National University, Seoul 08826, Korea
- Department of Physics, University of Seoul, Seoul 02504, Korea
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43
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de la Barrera SC, Sinko MR, Gopalan DP, Sivadas N, Seyler KL, Watanabe K, Taniguchi T, Tsen AW, Xu X, Xiao D, Hunt BM. Tuning Ising superconductivity with layer and spin-orbit coupling in two-dimensional transition-metal dichalcogenides. Nat Commun 2018; 9:1427. [PMID: 29650994 PMCID: PMC5897486 DOI: 10.1038/s41467-018-03888-4] [Citation(s) in RCA: 84] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2017] [Accepted: 03/20/2018] [Indexed: 12/01/2022] Open
Abstract
Systems simultaneously exhibiting superconductivity and spin–orbit coupling are predicted to provide a route toward topological superconductivity and unconventional electron pairing, driving significant contemporary interest in these materials. Monolayer transition-metal dichalcogenide (TMD) superconductors in particular lack inversion symmetry, yielding an antisymmetric form of spin–orbit coupling that admits both spin-singlet and spin-triplet components of the superconducting wavefunction. Here, we present an experimental and theoretical study of two intrinsic TMD superconductors with large spin–orbit coupling in the atomic layer limit, metallic 2H-TaS2 and 2H-NbSe2. We investigate the superconducting properties as the material is reduced to monolayer thickness and show that high-field measurements point to the largest upper critical field thus reported for an intrinsic TMD superconductor. In few-layer samples, we find the enhancement of the upper critical field is sustained by the dominance of spin–orbit coupling over weak interlayer coupling, providing additional candidate systems for supporting unconventional superconducting states in two dimensions. Monolayer transition-metal dichalcogenide (TMD) is promising to host features of topological superconductivity. Here, de la Barrera et al. study layered compounds, 2H-TaS2 and 2H-NbSe2, in their atomic layer limit and find a largest upper critical field for an intrinsic TMD superconductor.
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Affiliation(s)
| | - Michael R Sinko
- Department of Physics, Carnegie Mellon University, Pittsburgh, PA, 15213, USA
| | - Devashish P Gopalan
- Department of Physics, Carnegie Mellon University, Pittsburgh, PA, 15213, USA
| | - Nikhil Sivadas
- Department of Physics, Carnegie Mellon University, Pittsburgh, PA, 15213, USA.,School of Applied and Engineering Physics, Cornell University, Ithaca, NY, 14853, USA
| | - Kyle L Seyler
- Department of Physics, University of Washington, Seattle, WA, 98195, USA
| | - Kenji Watanabe
- Advanced Materials Laboratory, National Institute for Materials Science, Tsukuba, Ibaraki, 305-0044, Japan
| | - Takashi Taniguchi
- Advanced Materials Laboratory, National Institute for Materials Science, Tsukuba, Ibaraki, 305-0044, Japan
| | - Adam W Tsen
- Institute for Quantum Computing and Department of Chemistry, University of Waterloo, Waterloo, ON, N2L 3G1, Canada
| | - Xiaodong Xu
- Department of Physics, University of Washington, Seattle, WA, 98195, USA.,Department of Materials Science and Engineering, University of Washington, Seattle, WA, 98195, USA
| | - Di Xiao
- Department of Physics, Carnegie Mellon University, Pittsburgh, PA, 15213, USA
| | - Benjamin M Hunt
- Department of Physics, Carnegie Mellon University, Pittsburgh, PA, 15213, USA.
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44
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Full superconducting dome of strong Ising protection in gated monolayer WS 2. Proc Natl Acad Sci U S A 2018; 115:3551-3556. [PMID: 29555774 DOI: 10.1073/pnas.1716781115] [Citation(s) in RCA: 87] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Many recent studies show that superconductivity not only exists in atomically thin monolayers but can exhibit enhanced properties such as a higher transition temperature and a stronger critical field. Nevertheless, besides being unstable in air, the weak tunability in these intrinsically metallic monolayers has limited the exploration of monolayer superconductivity, hindering their potential in electronic applications (e.g., superconductor-semiconductor hybrid devices). Here we show that using field effect gating, we can induce superconductivity in monolayer WS2 grown by chemical vapor deposition, a typical ambient-stable semiconducting transition metal dichalcogenide (TMD), and we are able to access a complete set of competing electronic phases over an unprecedented doping range from band insulator, superconductor, to a reentrant insulator at high doping. Throughout the superconducting dome, the Cooper pair spin is pinned by a strong internal spin-orbit interaction, making this material arguably the most resilient superconductor in the external magnetic field. The reentrant insulating state at positive high gating voltages is attributed to localization induced by the characteristically weak screening of the monolayer, providing insight into many dome-like superconducting phases observed in field-induced quasi-2D superconductors.
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45
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Ma D, Ma B, Lu Z, He C, Tang Y, Lu Z, Yang Z. Interaction between H 2O, N 2, CO, NO, NO 2 and N 2O molecules and a defective WSe 2 monolayer. Phys Chem Chem Phys 2018; 19:26022-26033. [PMID: 28920598 DOI: 10.1039/c7cp04351a] [Citation(s) in RCA: 45] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
In this study, the interaction between gas molecules, including H2O, N2, CO, NO, NO2 and N2O, and a WSe2 monolayer containing an Se vacancy (denoted as VSe) has been theoretically studied. Theoretical results show that H2O and N2 molecules are highly prone to be physisorbed on the VSe surface. The presence of the Se vacancy can significantly enhance the sensing ability of the WSe2 monolayer toward H2O and N2 molecules. In contrast, CO and NO molecules highly prefer to be molecularly chemisorbed on the VSe surface with the non-oxygen atom occupying the Se vacancy site. Furthermore, the exposed O atoms of the molecularly chemisorbed CO or NO can react with additional CO or NO molecules, to produce C-doped or N-doped WSe2 monolayers. The calculated energies suggest that the filling of the CO or NO molecule and the removal of the exposed O atom are both energetically and dynamically favorable. Electronic structure calculations show that the WSe2 monolayers are p-doped by the CO and NO molecules, as well as the C and N atoms. However, only the NO molecule and N atom doped WSe2 monolayers exhibit significantly improved electronic structures compared with VSe. The NO2 and N2O molecules will dissociate directly to form an O-doped WSe2 monolayer, for which the defect levels due to the Se vacancy can be completely removed. The calculated energies suggest that although the dissociation processes for NO2 and N2O molecules are highly exothermic, the N2O dissociation may need to operate at an elevated temperature compared with room temperature, due to its large energy barrier of ∼1 eV.
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Affiliation(s)
- Dongwei Ma
- School of Physics
- Anyang Normal University
- Anyang 455000
- China
| | - Benyuan Ma
- Physics and Electronic Engineering College
- Nanyang Normal University
- Nanyang 473061
- China
| | - Zhiwen Lu
- Physics and Electronic Engineering College
- Nanyang Normal University
- Nanyang 473061
- China
| | - Chaozheng He
- Physics and Electronic Engineering College
- Nanyang Normal University
- Nanyang 473061
- China
| | - Yanan Tang
- College of Physics and Electronic Engineering
- Zhengzhou Normal University
- Zhengzhou
- China
| | - Zhansheng Lu
- College of Physics and Materials Science
- Henan Normal University
- Xinxiang 453007
- China
| | - Zongxian Yang
- College of Physics and Materials Science
- Henan Normal University
- Xinxiang 453007
- China
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46
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Cheng C, Sun JT, Chen XR, Meng S. Hidden spin polarization in the 1T-phase layered transition-metal dichalcogenides MX 2 (M = Zr, Hf; X = S, Se, Te). Sci Bull (Beijing) 2018; 63:85-91. [PMID: 36658929 DOI: 10.1016/j.scib.2017.12.003] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2017] [Revised: 10/24/2017] [Accepted: 11/30/2017] [Indexed: 01/21/2023]
Abstract
The recent discovery of hidden spin polarization emerging in layered materials of specific nonmagnetic crystal is a fascinating phenomenon, though hardly explored yet. Here, we have studied hidden spin textures in layered nonmagnetic 1T-phase transition-metal dichalcogenides MX2 (M = Zr, Hf; X = S, Se, Te) by using first-principles calculations. Spin-layer locking effect, namely, energy-degenerate opposite spins spatially separated in the top and bottom layer respectively, has been identified. In particular, the hidden spin polarization of β-band can be easily probed, which is strongly affected by the strength of spin-orbit coupling. The hidden spin polarization of ξ-band locating at high symmetry M point (conduction band minimum) has a strong anisotropy. In the bilayer, the hidden spin polarization is preserved at the upmost Se layer, while being suppressed if the ZrSe2 layer is taken as the symmetry partner. Our results on hidden spin polarization in 1T-phase dichalcogenides, verifiable by spin-resolved and angle-resolved photoemission spectroscopy (ARPES), enrich our understanding of spin physics and provide important clues to search for specific spin polarization in two dimensional materials for spintronic and quantum information applications.
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Affiliation(s)
- Cai Cheng
- Institute of Atomic and Molecular Physics, College of Physical Science and Technology, Sichuan University, Chengdu 610064, China; Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Jia-Tao Sun
- Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Xiang-Rong Chen
- Institute of Atomic and Molecular Physics, College of Physical Science and Technology, Sichuan University, Chengdu 610064, China.
| | - Sheng Meng
- Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China.
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47
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Hill HM, Rigosi AF, Krylyuk S, Tian J, Nguyen NV, Davydov AV, Newell DB, Walker ARH. Comprehensive optical characterization of atomically thin NbSe 2. PHYSICAL REVIEW. B 2018; 98:10.1103/PhysRevB.98.165109. [PMID: 30984898 PMCID: PMC6459197 DOI: 10.1103/physrevb.98.165109] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Transition-metal dichalcogenides (TMDCs) have offered experimental access to quantum confinement in one dimension. In recent years, metallic TMDCs like NbSe2 have taken center stage with many of them exhibiting interesting temperature-dependent properties such as charge density waves and superconductivity. In this paper, we perform a comprehensive optical analysis of NbSe2 by utilizing Raman spectroscopy, differential reflectance contrast, and spectroscopic ellipsometry. These analyses, when coupled with Kramers-Kronig analysis, allow us to extract the dielectric functions of bulk and atomically thin NbSe2 and relate them to the resonant behavior of the Raman spectra.
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Affiliation(s)
- Heather M. Hill
- Physical Measurement Laboratory, National Institute of
Standards and Technology, Gaithersburg, Maryland 20899, USA
| | - Albert F. Rigosi
- Physical Measurement Laboratory, National Institute of
Standards and Technology, Gaithersburg, Maryland 20899, USA
| | - Sergiy Krylyuk
- Material Measurement Laboratory, National Institute of
Standards and Technology, Gaithersburg, Maryland 20899, USA
- Theiss Research, Inc., La Jolla, California 92037,
USA
| | - Jifa Tian
- Physical Measurement Laboratory, National Institute of
Standards and Technology, Gaithersburg, Maryland 20899, USA
- Department of Physics and Astronomy, and Birck
Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, USA
| | - Nhan V. Nguyen
- Physical Measurement Laboratory, National Institute of
Standards and Technology, Gaithersburg, Maryland 20899, USA
| | - Albert V. Davydov
- Material Measurement Laboratory, National Institute of
Standards and Technology, Gaithersburg, Maryland 20899, USA
| | - David B. Newell
- Physical Measurement Laboratory, National Institute of
Standards and Technology, Gaithersburg, Maryland 20899, USA
| | - Angela R. Hight Walker
- Physical Measurement Laboratory, National Institute of
Standards and Technology, Gaithersburg, Maryland 20899, USA
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48
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Godin K, Cupo C, Yang EH. Reduction in Step Height Variation and Correcting Contrast Inversion in Dynamic AFM of WS 2 Monolayers. Sci Rep 2017; 7:17798. [PMID: 29259238 PMCID: PMC5736643 DOI: 10.1038/s41598-017-18077-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2017] [Accepted: 12/05/2017] [Indexed: 11/27/2022] Open
Abstract
A model has been developed to account for and prevent the anomalies encountered in topographic images of transition metal dichalcogenide monolayers using dynamic atomic force microscopy (dAFM). The height of WS2 monolayers measured using dAFM appeared to be increased or decreased, resulting from the interactions between the tip and the surface. The hydrophilic SiO2 substrate appeared higher than the weakly hydrophilic WS2 when the tip amplitude was low or at a high set point (high force). Large amplitudes and low set points corrected the step height inversion, but did not recover the true step height. Removing water from the sample resulted in an order of magnitude reduced variation in step height, but the WS2 appeared inverted except at low amplitudes and high set points. Our model explains the varying step heights in dAFM of TMDs as a result of varying tip-sample interactions between the sample and substrate, in the presence or absence of capillaries. To eliminate contrast inversion, high amplitudes can be used to reduce the effect of capillary forces. However, when capillaries are not present, low amplitudes and high set points produce images with proper contrast due to tool operation in the repulsive regime on both materials.
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Affiliation(s)
- Kyle Godin
- Department of Mechanical Engineering, Stevens Institute of Technology, Hoboken, New Jersey, 07030, United States
| | - Christian Cupo
- Department of Mechanical Engineering, Stevens Institute of Technology, Hoboken, New Jersey, 07030, United States
| | - Eui-Hyeok Yang
- Department of Mechanical Engineering, Stevens Institute of Technology, Hoboken, New Jersey, 07030, United States.
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Xing Y, Zhao K, Shan P, Zheng F, Zhang Y, Fu H, Liu Y, Tian M, Xi C, Liu H, Feng J, Lin X, Ji S, Chen X, Xue QK, Wang J. Ising Superconductivity and Quantum Phase Transition in Macro-Size Monolayer NbSe 2. NANO LETTERS 2017; 17:6802-6807. [PMID: 28967758 DOI: 10.1021/acs.nanolett.7b03026] [Citation(s) in RCA: 54] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Two-dimensional (2D) transition metal dichalcogenides (TMDs) have a range of unique physics properties and could be used in the development of electronics, photonics, spintronics, and quantum computing devices. The mechanical exfoliation technique of microsize TMD flakes has attracted particular interest due to its simplicity and cost effectiveness. However, for most applications, large-area and high-quality films are preferred. Furthermore, when the thickness of crystalline films is down to the 2D limit (monolayer), exotic properties can be expected due to the quantum confinement and symmetry breaking. In this paper, we have successfully prepared macro-size atomically flat monolayer NbSe2 films on bilayer graphene terminated surface of 6H-SiC(0001) substrates by a molecular beam epitaxy (MBE) method. The films exhibit an onset superconducting critical transition temperature (Tconset) above 6 K and the zero resistance superconducting critical transition temperature (Tczero) up to 2.40 K. Simultaneously, the transport measurements at high magnetic fields and low temperatures reveal that the parallel characteristic field Bc//(T = 0) is above 5 times of the paramagnetic limiting field, consistent with Zeeman-protected Ising superconductivity mechanism. Besides, by ultralow temperature electrical transport measurements, the monolayer NbSe2 film shows the signature of quantum Griffiths singularity (QGS) when approaching the zero-temperature quantum critical point.
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Affiliation(s)
- Ying Xing
- International Center for Quantum Materials, School of Physics, Peking University , Beijing 100871, China
- Beijing Key Laboratory of Optical Detection Technology for Oil and Gas, China University of Petroleum , Beijing 102249, China
- Collaborative Innovation Center of Quantum Matter , Beijing 100871, China
| | - Kun Zhao
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University , Beijing 100084, China
- Collaborative Innovation Center of Quantum Matter , Beijing 100871, China
| | - Pujia Shan
- International Center for Quantum Materials, School of Physics, Peking University , Beijing 100871, China
- Collaborative Innovation Center of Quantum Matter , Beijing 100871, China
| | - Feipeng Zheng
- International Center for Quantum Materials, School of Physics, Peking University , Beijing 100871, China
- Collaborative Innovation Center of Quantum Matter , Beijing 100871, China
| | - Yangwei Zhang
- International Center for Quantum Materials, School of Physics, Peking University , Beijing 100871, China
- Collaborative Innovation Center of Quantum Matter , Beijing 100871, China
| | - Hailong Fu
- International Center for Quantum Materials, School of Physics, Peking University , Beijing 100871, China
- Collaborative Innovation Center of Quantum Matter , Beijing 100871, China
| | - Yi Liu
- International Center for Quantum Materials, School of Physics, Peking University , Beijing 100871, China
- Collaborative Innovation Center of Quantum Matter , Beijing 100871, China
| | - Mingliang Tian
- High Magnetic Field Laboratory, Chinese Academy of Sciences , Hefei 230031, China
| | - Chuanying Xi
- High Magnetic Field Laboratory, Chinese Academy of Sciences , Hefei 230031, China
| | - Haiwen Liu
- Department of Physics, Beijing Normal University , Beijing 100875, China
| | - Ji Feng
- International Center for Quantum Materials, School of Physics, Peking University , Beijing 100871, China
- Collaborative Innovation Center of Quantum Matter , Beijing 100871, China
| | - Xi Lin
- International Center for Quantum Materials, School of Physics, Peking University , Beijing 100871, China
- Collaborative Innovation Center of Quantum Matter , Beijing 100871, China
| | - Shuaihua Ji
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University , Beijing 100084, China
- Collaborative Innovation Center of Quantum Matter , Beijing 100871, China
| | - Xi Chen
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University , Beijing 100084, China
- Collaborative Innovation Center of Quantum Matter , Beijing 100871, China
| | - Qi-Kun Xue
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University , Beijing 100084, China
- Collaborative Innovation Center of Quantum Matter , Beijing 100871, China
| | - Jian Wang
- International Center for Quantum Materials, School of Physics, Peking University , Beijing 100871, China
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University , Beijing 100084, China
- Collaborative Innovation Center of Quantum Matter , Beijing 100871, China
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